Golden rectangle

In geometry, a golden rectangle is a rectangle with side lengths in golden ratio ${\displaystyle {\tfrac {1+{\sqrt {5}}}{2}}:1,}$ or ⁠${\displaystyle \varphi :1,}$⁠ with ⁠${\displaystyle \varphi }$⁠ approximately equal to 1.618 or 89/55.

Golden rectangles exhibit a special form of self-similarity: if a square is added to the long side, or removed from the short side, the result is a golden rectangle as well.