A Golden Rectangle is a rectangle with proportions that are two consecutive numbers from the Fibonacci sequence. The example above, 1/2 is the most common, but Golden rectangles are all over the place--take 3 x 5 index cards, for example.

     If you split the Golden Rectangle into two triangles, they are called Golden Triangles. Using the Pythagorean Theorem, we can find the hypotenuse of the triangle: sqrt(5).

     The Greeks took this triangle and really cut loose. They moved around the pieces of the triangle to make a super Golden Rectangle:

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     This new Golden Rectangle had proportions of

Look familiar?