# Proving an equation

1. Mar 11, 2008

### Spahrtacus

1. The problem statement, all variables and given/known data
Prove that tan^2θ - sin^2θ = tan^2θsin^2θ

2. Relevant equations
I'm not sure :S

3. The attempt at a solution
I have no idea

2. Mar 11, 2008

### Kurdt

Staff Emeritus
What is the definition of tan?

3. Mar 11, 2008

### Spahrtacus

tan = sin^2θ/cos^2θ

?

4. Mar 11, 2008

### Kurdt

Staff Emeritus
$$\tan (\theta) = \frac{\sin(\theta)}{\cos(\theta)}$$

so

$$\tan^2 (\theta) = \frac{\sin^2(\theta)}{\cos^2(\theta)}$$

You will then need to manipulate one side until it equals the other using basic trigonometric identities.