The golden section is a rectangle of a shape such that the ratio of the length of the short side (B) to the long side (A) is the same as the ratio of the length of the long side (A) to the length of the long side (A) plus the length of the short side (B) It can be written as B : A = A : A+B or B : A=A : C. The ratio is approximately 5:8. The rectangle is also known as the golden rectangle.