Golden Ratio & Golden Section : : Golden Rectangle : : Golden Spiral
Golden Ratio & Golden Section
In mathematics and the arts, two quantities are in the golden ratio if the ratio between the sum of those quantities and the larger one is the same as the ratio between the larger one and the smaller.
Expressed algebraically:
The figure of a golden section illustrates the geometric relationship that defines this constant. The golden ratio is an irrational mathematical constant, approximately 1.6180339887.
Golden Rectangle
A golden rectangle is a rectangle whose side lengths are in the golden ratio, 1: j (one-to-phi),that is, 1 : or approximately 1:1.618.
A golden rectangle can be constructed with only
straightedge
and compass by this technique:
|
Golden Spiral
In geometry, a golden spiral is a logarithmic spiral whose growth factor b is related to j, the golden ratio. Specifically, a golden spiral gets wider (or further from its origin) by a factor of j for every quarter turn it makes.Successive points dividing a golden rectangle into squares lie on
a logarithmic spiral which is sometimes known as the golden spiral.
Image Source: http://mathworld.wolfram.com/GoldenRatio.html
Golden Ratio in Architecture and Art
Many architects and artists have proportioned their works to approximate the golden ratio—especially in the form of the golden rectangle, in which the ratio of the longer side to the shorter is the golden ratio—believing this proportion to be aesthetically pleasing. [Source: Wikipedia.org]
Here are few examples:
Parthenon, Acropolis, Athens.
This ancient temple fits almost precisely into a golden rectangle.
Source: http://britton.disted.camosun.bc.ca/goldslide/jbgoldslide.htm
The Vetruvian Man"(The Man in Action)" by Leonardo Da Vinci
We can draw many lines of the rectangles into this figure.
Then, there are three distinct sets of Golden Rectangles:
Each one set for the head area, the torso, and the legs.
Image Source >>
Golden Ratio in Nature
Adolf Zeising, whose main interests were mathematics and philosophy, found the golden ratio expressed in the arrangement of branches along the stems of plants and of veins in leaves. He extended his research to the skeletons of animals and the branchings of their veins and nerves, to the proportions of chemical compounds and the geometry of crystals, even to the use of proportion in artistic endeavors. In these phenomena he saw the golden ratio operating as a universal law.[38] Zeising wrote in 1854:The Golden Ratio is a universal law in which is contained the ground-principle of all formative striving for beauty and completeness in the realms of both nature and art, and which permeates, as a paramount spiritual ideal, all structures, forms and proportions, whether cosmic or individual, organic or inorganic, acoustic or optical; which finds its fullest realization, however, in the human form.
Examples:
Click on the picture for animation showing more examples of golden ratio.
Source: http://www.xgoldensection.com/xgoldensection.html
A slice through a Nautilus shell reveals
golden spiral construction principle.
FIBONACCI NUMBERS
About Fibonacci
Fibonacci was known in his time and is still recognized today as the "greatest European mathematician of the middle ages." He was born in the 1170's and died in the 1240's and there is now a statue commemorating him located at the Leaning Tower end of the cemetery next to the Cathedral in Pisa. Fibonacci's name is also perpetuated in two streetsthe quayside Lungarno Fibonacci in Pisa and the Via Fibonacci in Florence.
His full name was Leonardo of Pisa, or Leonardo Pisano in Italian since he was born in Pisa. He called himself Fibonacci which was short for Filius Bonacci, standing for "son of Bonacci", which was his father's name. Leonardo's father( Guglielmo Bonacci) was a kind of customs officer in the North African town of Bugia, now called Bougie. So Fibonacci grew up with a North African education under the Moors and later travelled extensively around the Mediterranean coast. He then met with many merchants and learned of their systems of doing arithmetic. He soon realized the many advantages of the "Hindu-Arabic" system over all the others. He was one of the first people to introduce the Hindu-Arabic number system into Europe-the system we now use today- based of ten digits with its decimal point and a symbol for zero: 1 2 3 4 5 6 7 8 9. and 0
His book on how to do arithmetic in the decimal system, called Liber abbaci (meaning Book of the Abacus or Book of calculating) completed in 1202 persuaded many of the European mathematicians of his day to use his "new" system. The book goes into detail (in Latin) with the rules we all now learn in elementary school for adding, subtracting, multiplying and dividing numbers altogether with many problems to illustrate the methods in detail. ( http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibnat.html#Rabbits )
Fibonacci Numbers
The sequence, in which each number is the sum of the two preceding numbers is known as the Fibonacci series: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, ... (each number is the sum of the previous two).The ratio of successive pairs is so-called golden section (GS) - 1.618033989 . . . . .
whose reciprocal is 0.618033989 . . . . . so that we have 1/GS = 1 + GS.
The Fibonacci sequence, generated by the rule f1 = f2 = 1 , fn+1 = fn + fn-1,
is well known in many different areas of mathematics and science.
Pascal's Triangle and Fibonacci Numbers
The triangle was studied by B. Pascal, although it had been described centuries earlier by Chinese mathematician Yanghui (about 500 years earlier, in fact) and the Persian astronomer-poet Omar Khayyám.
Pascal's Triangle is described by the following
formula:
where
is a binomial
coefficient.
The "shallow diagonals" of Pascal's
triangle
sum to Fibonacci numbers.
It is quite amazing that the Fibonacci number patterns occur so
frequently in naturesum to Fibonacci numbers.
( flowers, shells, plants, leaves, to name a few) that this phenomenon appears to be one of the principal "laws of nature". Fibonacci sequences appear in biological settings, in two consecutive Fibonacci numbers, such as branching in trees, arrangement of leaves on a stem, the fruitlets of a pineapple, the flowering of artichoke, an uncurling fern and the arrangement of a pine cone. In addition, numerous claims of Fibonacci numbers or golden sections in nature are found in popular sources, e.g. relating to the breeding of rabbits, the spirals of shells, and the curve of waves The Fibonacci numbers are also found in the family tree of honeybees.
Fibonacci and Nature
Plants do not know about this sequence - they just grow in the most efficient ways. Many plants show the Fibonacci numbers in the arrangement of the leaves around the stem. Some pine cones and fir cones also show the numbers, as do daisies and sunflowers. Sunflowers can contain the number 89, or even 144. Many other plants, such as succulents, also show the numbers. Some coniferous trees show these numbers in the bumps on their trunks. And palm trees show the numbers in the rings on their trunks.
Why do these arrangements occur? In the case of leaf arrangement,
or phyllotaxis, some of the cases may be related to maximizing the
space for each leaf, or the average amount of light falling on each
one. Even a tiny advantage would come to dominate, over many
generations. In the case of close-packed leaves in cabbages and
succulents the correct arrangement may be crucial for availability
of space. This is well described in several books listed here
>>
So nature isn't trying to use the Fibonacci numbers: they are
appearing as a by-product of a deeper physical process. That is why
the spirals are imperfect.
The plant is responding to physical constraints, not to a mathematical rule.
The plant is responding to physical constraints, not to a mathematical rule.
The basic idea is that the position of each new growth is about
222.5 degrees away from the previous one, because it provides, on
average, the maximum space for all the shoots. This angle is called
the golden angle, and it divides the complete 360 degree circle in
the golden section, 0.618033989 . . . .
Examples of the Fibonacci sequence in
nature.
Petals on flowers*
Probably most of us have never taken the time to examine very carefully the number or arrangement of petals on a flower. If we were to do so, we would find that the number of petals on a flower, that still has all of its petals intact and has not lost any, for many flowers is a Fibonacci number:- 3 petals: lily, iris
- 5 petals: buttercup, wild rose, larkspur, columbine (aquilegia)
- 8 petals: delphiniums
- 13 petals: ragwort, corn marigold, cineraria,
- 21 petals: aster, black-eyed susan, chicory
- 34 petals: plantain, pyrethrum
- 55, 89 petals: michaelmas daisies, the asteraceae family
* Read the entire article here:
http://britton.disted.camosun.bc.ca/fibslide/jbfibslide.htm
http://britton.disted.camosun.bc.ca/fibslide/jbfibslide.htm
Related Links:
http://britton.disted.camosun.bc.ca/jbfunpatt.htm
http://britton.disted.camosun.bc.ca/jbfunpatt.htm
Flower Patterns and Fibonacci Numbers
Why is it that the number of petals in a flower is often one of the following numbers: 3, 5, 8, 13, 21, 34 or 55? For example, the lily has three petals, buttercups have five of them, the chicory has 21 of them, the daisy has often 34 or 55 petals, etc. Furthermore, when one observes the heads of sunflowers, one notices two series of curves, one winding in one sense and one in another; the number of spirals not being the same in each sense. Why is the number of spirals in general either 21 and 34, either 34 and 55, either 55 and 89, or 89 and 144? The same for pinecones : why do they have either 8 spirals from one side and 13 from the other, or either 5 spirals from one side and 8 from the other? Finally, why is the number of diagonals of a pineapple also 8 in one direction and 13 in the other?Are these numbers the product of chance? No! They all belong to the Fibonacci sequence: 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, etc. (where each number is obtained from the sum of the two preceding). A more abstract way of putting it is that the Fibonacci numbers fn are given by the formula f1 = 1, f2 = 2, f3 = 3, f4 = 5 and generally f n+2 = fn+1 + fn . For a long time, it had been noticed that these numbers were important in nature, but only relatively recently that one understands why. It is a question of efficiency during the growth process of plants.
The explanation is linked to another famous number, the golden mean, itself intimately linked to the spiral form of certain types of shell. Let's mention also that in the case of the sunflower, the pineapple and of the pinecone, the correspondence with the Fibonacci numbers is very exact, while in the case of the number of flower petals, it is only verified on average (and in certain cases, the number is doubled since the petals are arranged on two levels).
© All rights reserved.
THE EFFECTIVENESS OF THE GOLDEN MEAN
The explanation which follows is very succinct. For a much more detailed explanation, with very interesting animations, see the web site in the reference.
In many cases, the head of a flower is made up of small seeds which are produced at the centre, and then migrate towards the outside to fill eventually all the space (as for the sunflower but on a much smaller level). Each new seed appears at a certain angle in relation to the preceeding one. For example, if the angle is 90 degrees, that is 1/4 of a turn, the result after several generations is that represented by figure 1.
In order to optimize the filling, it is necessary to choose the most irrational number there is, that is to say, the one the least well approximated by a fraction. This number is exactly the golden mean. The corresponding angle, the golden angle, is 137.5 degrees. (It is obtained by multiplying the non-whole part of the golden mean by 360 degrees and, since one obtains an angle greater than 180 degrees, by taking its complement). With this angle, one obtains the optimal filling, that is, the same spacing between all the seeds (figure 3).
This angle has to be chosen very precisely: variations of 1/10 of a degree destroy completely the optimization. (In fig 2, the angle is 137.6 degrees!) When the angle is exactly the golden mean, and only this one, two families of spirals (one in each direction) are then visible: their numbers correspond to the numerator and denominator of one of the fractions which approximates the golden mean : 2/3, 3/5, 5/8, 8/13, 13/21, etc.
These numbers are precisely those of the Fibonacci sequence (the bigger the numbers, the better the approximation) and the choice of the fraction depends on the time laps between the appearance of each of the seeds at the center of the flower.
This is why the number of spirals in the centers of sunflowers, and in the centers of flowers in general, correspond to a Fibonacci number. Moreover, generally the petals of flowers are formed at the extremity of one of the families of spiral. This then is also why the number of petals corresponds on average to a Fibonacci number.
REFERENCES:
-
An excellent Internet site of Ron Knot's at the University of Surrey on this and related topics.
-
S. Douady et Y. Couder, La physique des spirales végétales, La Recherche, janvier 1993, p. 26 (In French).
Source of the above segment:
http://www.popmath.org.uk/rpamaths/rpampages/sunflower.html
© Mathematics and Knots, U.C.N.W.,Bangor, 1996 - 2002
http://www.popmath.org.uk/rpamaths/rpampages/sunflower.html
© Mathematics and Knots, U.C.N.W.,Bangor, 1996 - 2002
Fibonacci numbers in vegetables and fruit
Romanesque Brocolli/Cauliflower (or Romanesco) looks and tastes like a cross between brocolli and cauliflower. Each floret is peaked and is an identical but smaller version of the whole thing and this makes the spirals easy to see.
Brocolli/Cauliflower
© All rights reserved Image Source >>
© All rights reserved Image Source >>
* * *
Human Hand
Every human has two hands, each one of these has five fingers, each finger has three parts which are separated by two knuckles. All of these numbers fit into the sequence. However keep in mind, this could simply be coincidence.Human Face
Knowledge of the golden section, ratio and rectangle goes back to the Greeks, who based their most famous work of art on them: the Parthenon is full of golden rectangles. The Greek followers of the mathematician and mystic Pythagoras even thought of the golden ratio as divine.
Later, Leonardo da Vinci painted Mona Lisa's face to
fit perfectly into a golden rectangle, and structured the rest of
the painting around similar rectangles.
Mozart divided a striking number of his sonatas into
two parts whose lengths reflect the golden ratio, though there is
much debate about whether he was conscious of this. In more modern
times, Hungarian composer Bela Bartok and French architect Le
Corbusier purposefully incorporated the golden ratio into their
work.
Even today, the golden ratio is in human-made objects all around
us. Look at almost any Christian cross; the ratio of the vertical
part to the horizontal is the golden ratio. To find a golden
rectangle, you need to look no further than the credit cards in your
wallet.Despite these numerous appearances in works of art throughout the ages, there is an ongoing debate among psychologists about whether people really do perceive the golden shapes, particularly the golden rectangle, as more beautiful than other shapes. In a 1995 article in the journal Perception, professor Christopher Green,
of York University in Toronto, discusses several experiments over the years that have shown no measurable preference for the golden rectangle, but notes that several others have provided evidence suggesting such a preference exists.
Regardless of the science, the golden ratio retains a mystique, partly because excellent approximations of it turn up in many unexpected places in nature. The spiral inside a nautilus shell is remarkably close to the golden section, and the ratio of the lengths of the thorax and abdomen in most bees is nearly the golden ratio. Even a cross section of the most common form of human DNA fits nicely into a golden decagon. The golden ratio and its relatives also appear in many unexpected contexts in mathematics, and they continue to spark interest in the mathematical community.
Dr. Stephen Marquardt, a former plastic surgeon, has used the golden section, that enigmatic number that has long stood for beauty, and some of its relatives to make a mask that he claims is the most beautiful shape a human face can have.
The Mask of a perfect human face
Egyptian Queen Nefertiti (1400 B.C.)
An artist's impression of the face of Jesus
based on the Shroud of Turin and corrected
to match Dr. Stephen Marquardt's mask.
Click here for more detailed analysis.
based on the Shroud of Turin and corrected
to match Dr. Stephen Marquardt's mask.
Click here for more detailed analysis.
"Averaged" (morphed) face of few
celebrities.
Related website: http://www.faceresearch.org/tech/demos/average
Related website: http://www.faceresearch.org/tech/demos/average
You can overlay the Repose
Frontal Mask (also called the RF Mask or Repose Expression –
Frontal View Mask) over a photograph of your own face to help you
apply makeup, to aid in evaluating your face for
face lift surgery, or
simply to see how much your face conforms to the measurements of the
Golden Ratio.
Visit Dr.
Marquardt's Web site for more information on the beauty
mask.Source of the above article (with exception of few added photos):
http://tlc.discovery.com/convergence/humanface/articles/mask.html
Related links:
-
Dr. Marquardt's Web site
Related websites
Fibonacci's Rabbits
The original problem that Fibonacci investigated, in the year 1202, was about how fast rabbits could breed in ideal circumstances. "A pair of rabbits, one month old, is too young to reproduce. Suppose that in their second month, and every month thereafter, they produce a new pair. If each new pair of rabbits does the same, and none of the rabbits dies, how many pairs of rabbits will there be at the beginning of each month?"- At the end of the first month, they mate, but there is still one only 1 pair.
- At the end of the second month the female produces a new pair, so now there are 2 pairs of rabbits in the field.
- At the end of the third month, the original female produces a second pair, making 3 pairs in all in the field.
- At the end of the fourth month, the original female has produced yet another new pair, the female born two months ago produces her first pair also, making 5 pairs. (http://www.mcs.surrey.ac.uk/Personal/R.Knott/Fibonacci/fibBio.html)
The Fibonacci Rectangles and Shell Spirals
We can make another picture showing the Fibonacci numbers 1,1,2,3,5,8,13,21,.. if we start with two small squares of size 1 next to each other. On top of both of these draw a square of size 2 (=1+1).The next diagram shows that we can draw a spiral by putting together quarter circles, one in each new square. This is a spiral (the Fibonacci Spiral). A similar curve to this occurs in nature as the shape of a snail shell or some sea shells. Whereas the Fibonacci Rectangles spiral increases in size by a factor of Phi (1.618..) in a quarter of a turn (i.e. a point a further quarter of a turn round the curve is 1.618... times as far from the centre, and this applies to all points on the curve), the Nautilus spiral curve takes a whole turn before points move a factor of 1.618... from the centre.
A slice through a Nautilus shell
Here is a curve which crosses the X-axis at the
Fibonacci numbers
The spiral part crosses at 1 2 5 13 etc on the positive axis, and
0 1 3 8 etc on the negative axis. The oscillatory part crosses at 0
1 1 2 3 5 8 13 etc on the positive axis. The curve is strangely
reminiscent of the shells of Nautilus and snails. This is not
surprising, as the curve tends to a logarithmic spiral as it
expands.
Nautilus shell (cut)
© All rights reserved. Image source >>
© All rights reserved. Image source >>
Proportion - Golden Ratio and Rule of Thirds
© R. Berdan 20/01/2004.
Published with permission of the author
Proportion refers the size relationship of visual elements to each other and to the whole picture. One of the reasons proportion is often considered important in composition is that viewers respond to it emotionally. Proportion in art has been examined for hundreds of years, long before photography was invented. One proportion that is often cited as occurring frequently in design is the Golden mean or Golden ratio.
Golden Ratio: 1, 1, 2, 3, 5, 8, 13, 21, 34 etc. Each succeeding number after 1 is equal to the sum of the two preceding numbers. The Ratio formed 1:1.618 is called the golden mean - the ratio of bc to ab is the same as ab to ac. If you divide each smaller window again with the same ratio and joing their corners you end up with a logarithmic spiral. This spiral is a motif found frequently throughout nature in shells, horns and flowers (and my Science & Art logo).
tlc.discovery.com/convergence/humanface/articles/mask.html
Rule of thirds grid applied to a landscape |
|
Golden mean grid applied a simple composition |
In summary, proportion is an element of design you should always be aware of but you must also realize that other design factors along with your own unique sensitivity about the subject dictates where you should place items in the viewfinder. Understanding proportion and various elements of design are guidelines only and you should always follow your instincts combined with your knowledge. Never be afraid to experiment and try something drastically different, and learn from both your successes and failures. Also try to be open minded about new ways of taking pictures, new techniques, ideas - surround yourself with others that share an open mind and enthusiasm and you will improve your compositional skills quickly.
Note: The above segment is part of the article COMPOSITION & the ELEMENTS of VISUAL DESIGN by Robert Berdan ( http://www.scienceandart.org/ )
© R. Berdan 20/01/2004
Published with permission of the author.
The entire article can be found here (PDF):
http://www.scienceandart.org/photography/elementsofdesign.pdf
The entire article can be found here (PDF):
http://www.scienceandart.org/photography/elementsofdesign.pdf
Subject Related Links and Resources
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BLUEPRINTS OF THE COSMOS - by Christine Sterne *****/*****
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Nature's Patterns Photo CD 50 Royalty Free Images
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Bogomolny, A. "Golden Ratio in Geometry."
http://www.cut-the-knot.org/do_you_know/GoldenRatio.shtml -
Hofstetter, K. "A Simple Construction of the Golden Ratio." Forum Geom. 2, 65-66, 2002. http://forumgeom.fau.edu/FG2002volume2/FG200208index.html.
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Hofstetter, K. "A 4-Step Construction of the Golden Ratio." Forum Geom. 6, 179-180, 2006. http://forumgeom.fau.edu/FG2006volume6/FG200618index.html.
-
Olariu, A. "Golden Section and the Art of Painting." 18 Aug 1999. http://arxiv.org/abs/physics/9908036/.
-
Weisstein, E. W. "Books about Golden Ratio."
http://www.ericweisstein.com/encyclopedias/books/GoldenRatio.html
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- A Timeline of Mathematicians
- History topics
- A History of Pi
- THE GOD OF ABRAHAM: A Mathematician's View
- Lore and Order: Learning from the Ancients
- Astronomic and Cosmographic Data
Subject Related Resources: Books, Magazines, DVDs
The Self-Made Tapestry: Pattern Formation in Nature by Philip Ball Oxford Press; Reprint edition (August 2001) |
|
This deep, beautiful exploration of the recurring
patterns that we find both in the living and inanimate worlds
will change how you think about everything from evolution to
earthquakes. Not by any means a simple book, it is still
completely engaging; even the occasional forays into
mathematics and the abstractions of hydrodynamics are
endurable, tucked as they are between Ball's bright prose and
his hundreds of carefully selected illustrations.
When speaking of the living world, Ball seeks to go beyond the theory of natural selection, which explains why we see certain characteristics (height, shape, camouflage), to find mechanisms that can explain how such characteristics come to be. Again, this is no easy task, but for those willing to follow his discussion, the elegance of nature is laid out in zebras' stripes, ivy leaves, and butterfly wings. Moving on to find the same patterns at work in the clouds of Jupiter and the cracks in the San Andreas fault give strength to the feeling that there are self-composing structures that guide everything in the universe toward a kind of order. |
|
Mathematics
in Nature: Modeling Patterns in the Natural World by John A.
Adam Princeton Univ Pr; (November 10, 2003) |
|
From rainbows, river meanders, and shadows to
spider webs, honeycombs, and the markings on animal coats, the
visible world is full of patterns that can be described
mathematically. Examining such readily observable phenomena,
this book introduces readers to the beauty of nature as
revealed by mathematics and the beauty of mathematics as
revealed in nature.
Generously illustrated, written in an informal style, and replete with examples from everyday life, Mathematics in Nature is an excellent and undaunting introduction to the ideas and methods of mathematical modeling. It illustrates how mathematics can be used to formulate and solve puzzles observed in nature and to interpret the solutions. In the process, it teaches such topics as the art of estimation and the effects of scale, particularly what happens as things get bigger. Readers will develop an understanding of the symbiosis that exists between basic scientific principles and their mathematical expressions as well as a deeper appreciation for such natural phenomena as cloud formations, halos and glories, tree heights and leaf patterns, butterfly and moth wings, and even puddles and mud cracks. Developed out of a university course, this book makes an ideal supplemental text for courses in applied mathematics and mathematical modeling. It will also appeal to mathematics educators and enthusiasts at all levels, and is designed so that it can be dipped into at leisure. |
|
The
Golden Ratio: The Story of Phi, the World's Most Astonishing
Number (2002) by Mario Livio |
|
Math
in Science and Nature: Finding Patterns in the World Around
Us (1999) by Robert Gardner, Edward A. Shore |
|
The
Curves of Life (1979) Theodore A Cook, Dover books |
|
On Growth and Form (1992) by D'Arcy Thompson |
|
Life's
Other Secret: The New Mathematics of the Living World
(1999) by Ian Stewart |
|
The Parsimonious Universe: Shape and Form in the Natural World
by Stefan Hildebrandt, Anthony Tromba |
|
Gamma: Exploring the Euler's Constant by Julian Havil (Author) Princeton Univ Pr; (March 17, 2003) |
|
N/A
|
Patterns in Nature (1974/79) by Peter S Stevens |
Nature's
Patterns Photo CD
50 Royalty Free* Images
Each image on the CD is 14 MB in size
(approx. 9 x 6 inches x 300 dpi) suitable for printing, multimedia and the web. |
|
Science Photo CD 50 science related images - Royalty Free
Each image on the CD is 14 MB in size
(approx. 9 x 6 inches x 300 dpi) suitable for printing, multimedia and the web. |
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Boyer, C. B. History of Mathematics. New York: Wiley, p. 56, 1968.
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Brown, D. The Da Vinci Code. New York: Doubleday, 2003.
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Coxeter, H. S. M. "The Golden Section, Phyllotaxis, and Wythoff's Game." Scripta Mathematica 19, 135-143, 1953.
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Dixon, R. Mathographics. New York: Dover, pp. 30-31 and 50, 1991.
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Finch, S. R. "The Golden Mean." §1.2 in Mathematical Constants. Cambridge, England: Cambridge University Press, pp. 5-12, 2003.
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Gardner, M. "Phi: The Golden Ratio." Ch. 8 in The Second Scientific American Book of Mathematical Puzzles & Diversions, A New Selection. New York: Simon and Schuster, pp. 89-103, 1961.
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Livio, M. The Golden Ratio: The Story of Phi, the World's Most Astonishing Number. New York: Broadway Books, 2002.
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van Zanten, A. J. "The Golden Ratio in the Arts of Painting, Building, and Mathematics." Nieuw Arch. Wisk. 17, 229-245, 1999.
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Walser, R. Der Goldene Schnitt. Stuttgart, Germany: Teubner, 1993.
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Wells, D. The Penguin Dictionary of Curious and Interesting Numbers. Middlesex, England: Penguin Books, pp. 36-49, 1986.
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