The golden number in geometry
Golden ratio, also known as the golden section, golden mean, or divine proportion, in mathematics, the irrational number (1 + Square root of√5)/2, often denoted by the Greek letter ϕ or τ, which is approximately equal to 1.618.
THE GOLDEN RECTANGLE
The golden rectangle is a rectangle that can be cut up into a square and a rectangle similar to the original one. In other words, it is that the rectangle that when subtracting the image of a square equal to that of its smaller side, the resulting rectangle is also a golden rectangle.
Considering a regular pentagon with two non-intersecting diagonals and taking into account what we already derived above, it follows that the length of the side equals the greatest part of the diagonal divided by the golden section.
