The golden ratio, also known as the golden proportion, golden mean, golden section, golden number, and divine proportion is the division of a given unit of length into two parts such that the ratio of the shorter to the longer equals the ratio of the longer part to the whole or, when a line is divided such that the ratio of the longer part of the line to the whole is exactly the same ratio as the shorter part of the line is to the longer part.
DaVinci's "The Vitruvian Man" illustrated the Golden Ratio of the human body.
The Golden Rectangle can be used to create a spiral, the Golden Spiral (also see Fibonacci Sequence). Starting with one Golden Rectangle, a second Golden Rectangle can be attached to the first using the longest side of the rectangle, side A as the shortest side B of the next rectangle. To this end the second rectangle is constructed 90 degrees perpendicular to the first rectangle. If this process is continued, called the spiraling of the Golden Rectangle, a curved line can be drawn through the corners of the rectangles creating the Golden Mean spiral. The spiraling of the Golden Mean spiral continues indefinitely in inward and outward directions, it's getting smaller and smaller spiraling inwards and getting bigger and bigger spiraling outwards.
For more information, see this page:http://www.tokenrock.com/explain-golden-ratio-177.html
STUDENTS: OPTIONAL sample of the Golden Ratio or Fibonacci Sequence.
If you post, you will receive extra credit for it. It is not required, but READ and UNDERSTAND these concepts. (This should be a review from studio art courses.)