Golden ratio
From specialfunctionswiki
The golden ratio $\varphi$ is the irrational algebraic number $$\varphi = \dfrac{1+\sqrt{5}}{2}.$$
Properties
Relationship between sine, imaginary number, logarithm, and the golden ratio Relationship between cosine, imaginary number, logarithm, and the golden ratio
Videos
The Golden Ratio & Fibonacci Numbers: Fact versus Fiction