# Math Help - Trig

1. ## Trig

If $tan A=\ sec2\alpha\ cot\pi$ prove that $\frac{cos(A+\pi)}{cos(A-\pi)}=-tan^2 \alpha$ I tried this by simplifying the statement and finally i get $\frac{cos(A - \pi)}{cosAcos\pi}=\frac{2cos^2\alpha}{2cos^2\alpha-1}$ then i can't simplify this prove.please help me!!!

2. ## Re: Trig

do you mean by $\pi$ the known pi or it is just another constant if it is the known pi then

$\cot \pi$ is undefind

3. ## Re: Trig

Originally Posted by srirahulan
If $tan A=\ sec2\alpha\ cot\pi$
is that secant supposed to be squared?

4. ## Re: Trig

pi is a constant.i am really sorry to undefind it.

5. ## Re: Trig

The question doesn't seem to make much sense anyway, doesn't $\frac{\cos(A+\pi)}{\cos(A-\pi)}=1$ ?

6. ## Re: Trig

Well, IF you meant sec squared(you didn't get back to me, so idk), then maybe This looks like it's getting somewhere

it looks like the right side will reduce to -1, so you can substitute in that cos(A+pi)/cos(A-pi) = 1 from above