Doubling identity for cosh (2)

Theorem

The following formula holds: $$\cosh(2z)=2\sinh^2(z)+1,$$ where $\cosh$ denotes hyperbolic cosine and $\sinh$ denotes hyperbolic sine.

References

• 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $4.5.32$