Question

How do you evaluate `sec(sec^-1(1/3))`?

Answer 1

You can't, at least not with real numbers.

Explanation:

The expression `sec^{-1}(1/3)` means find `x` so that `sec x=1/3`. But for all real numbers `x`, `sec x=1/(cos x)` has an absolute value greater than or equal to `1`.