A function f(x) is even if f(x) = f(-x)

`cosh x = (e^x + e^(-x))/2`

`cosh(-x) = (e^(-x) + e^-(-x))/2`

=> `(e^-x + e^x)/2`

As can be seen f(x) = f(-x).

**This proves that cosh(x) is an even function.**

A function f(x) is even if f(x) = f(-x)

`cosh x = (e^x + e^(-x))/2`

`cosh(-x) = (e^(-x) + e^-(-x))/2`

=> `(e^-x + e^x)/2`

As can be seen f(x) = f(-x).

**This proves that cosh(x) is an even function.**