Hyperbolic Cosine Function is Even

Theorem
Let $\cosh: \C \to \C$ be the hyperbolic cosine function on the set of complex numbers.

Then $\cosh$ is even:
 * $\map \cosh {-x} = \cosh x$

Also see

 * Hyperbolic Sine Function is Odd
 * Hyperbolic Tangent Function is Odd
 * Hyperbolic Cotangent Function is Odd
 * Hyperbolic Secant Function is Even
 * Hyperbolic Cosecant Function is Odd


 * Cosine Function is Even