1. ## Trigonometric Functions

Find tanØ if 9sin^2Ø - cos^2Ø =7

I have divided through with cos^2Ø

Giving me:

9tan^2Ø - 1 = 7sec^2Ø

But I am unsure on how to proceed from there.

The books answer gives it as: tanØ = ±2

2. ## Re: Trigonometric Functions

$\sec^2(\theta) = 1 + \tan^2(\theta)$

make that substitution and then let $u=\tan(\theta)$

solve the resulting quadratic in $u$ and substitute $\tan(\theta)$ back in.