cosh

\cosh, or hyperbolic cosine, is defined like this:

\cosh x=\frac{e^x+e^{-x}}2

It’s pronounced ‘cosh’ - as it’s spelt.

Finding from \tanh

Using the definition for \tanh:

\tanh=\frac{\sinh}{\cosh}

…we can deduce that:

\cosh=\frac{\sinh}{\tanh}