Trig: How does this equal one?

$ tan^2 \theta - sec^2 \theta = 1 $

Question

Trig: How does this equal one?

$ tan^2 \theta - sec^2 \theta = 1 $

anonymous · Answer

I have 

$ tan^2 \theta - sec^2 \theta = 1 $ 
$ \frac{sin^2 \theta}{cos^2 \theta} - \frac{1}{cos^2 \theta} $ 

I am stuck here

anonymous · Answer

I think I got it

astrophysics · Answer

It shouldn't

anonymous · Answer

Let me know if this is correct




$ tan^2 \theta - sec^2 \theta = 1 $ 
$ \frac{sin^2 \theta}{cos^2 \theta} - \frac{1}{cos^2 \theta} $ 
$ \frac{1+cos^2 \theta}{cos^2 \theta} - \frac{1}{cos^2 \theta} $ 
$ \frac{cos^2 \theta}{cos^2 \theta} = 1 $

freckles · Answer

do you mean -1?
recall
$$\sin^2(\theta)+\cos^2(\theta)=1 $$
divide both sides by cos^2(theta)
(this equation comes |dw:1434076836880:dw|)