If you have a function such that the value of the function at , namely is defined by some expression involving , then you evaluate by replacing in the definition of with a and then doing the arithmetic.
Just as an example, let's define . Given that definition, , whereas . Of course, you need to do the arithmetic and simplify, but the concept is simply that you replace the independent variable by whatever is in the parentheses following the function identifier.
Therefore, if someone says, evaluate where , you replace the variable with , thus:
And the same idea to evaluate which would look like:
So you need to write out your and then replace the independent variable, , with the definition of . And then simplify, of course.
My calculator said it, I believe it, that settles it