Doubling identity for cosh (1)
From specialfunctionswiki
Theorem
The following formula holds: $$\cosh(2z)=2\cosh^2(z)-1,$$ where $\cosh$ denotes hyperbolic cosine.
Proof
References
- 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $4.5.32$
