# How do you simplify #(sec(x))^2−1#?

##### 1 Answer

Sep 7, 2015

Using the Pythagorean identity:

#### Explanation:

This is an application of the Pythagorean identities, namely:

This can be derived from the standard Pythagorean identity by dividing everything by

From this identity, we can rearrange the terms to arrive at the answer to your question.

It would help you in the future to know all three versions of the Pythagorean identities:

If you forget these, just remember how to derive them: by dividing by either