# Math Help - Basic Trig problem

1. ## Basic Trig problem

Simplify and write the trigonometric expression in terms of sine and cosine:

I put this as my answer
(it looks like a formula that returns a number) I am figuring I have to reduce this?

2. ## Re: Basic Trig problem

The answer is actually -1. To show this, we have

$\tan^2 x - \sec^2 x = \frac{\sin^2 x}{\cos^2 x} - \frac{1}{\cos^2 x}$

$= \frac{\sin^2 x - 1}{\cos^2 x}$

$= \frac{-\cos^2 x}{\cos^2 x}$

$= -1$