# Math Help - Proofs

1. ## Proofs

I need to prove the following:

1) (1 + cotX)/(cosecX) - (secX)/(tanX + cotA) = cos

and

2) (5 - 7cos^2X)(sin^2X) = 5 - 2cot^2X

2. Originally Posted by Gilesy
I need to prove the following:

1) (1 + cotX)/(cosecX) - (secX)/(tanX + cotA) = cos

and

2) (5 - 7cos^2X)(sin^2X) = 5 - 2cot^2X
Replace all trig functions by the equivalent in terms of sines and cosines and simplify.

RonL

3. Originally Posted by Gilesy
[snip]
2) (5 - 7cos^2X)(sin^2X) = 5 - 2cot^2X
Note that the numerator can be written as $5 - 5 \cos^2 x - 2 \cos^2 x = 5(1 - \cos^2 x) - 2 \cos^2 x = 5 \sin^2 x - 2 \cos^2 x$.