Relationship between sech and sec
From specialfunctionswiki
Theorem
The following formula holds: $$\mathrm{sech}(z)=\sec(iz),$$ where $\mathrm{sech}$ denotes the hyperbolic secant and $\sec$ denotes the secant.
Proof
References
- 1964: Milton Abramowitz and Irene A. Stegun: Handbook of mathematical functions ... (previous) ... (next): $4.5.11$