If cosA is not equal to 1, then sin^2A/(1-cosA) =

If cosA is not equal to 1, then sin^2A/(1-cosA) =

A) 1 + cosA
B) cosA
C) 1-cosA
D) 1
E) cosA -1

Remember the mother of all trig identities:

$\sin^2 A + \cos^2 A = 1$

The minute you see that $\sin^2 A$ in there you should be thinking of that identity. Rearrange it so that you can do some substituting:

$\sin^2 A =1- \cos^2 A$

Now here’s what you’re working with:

$\dfrac{1- \cos^2 A}{1- \cos A}$

Now let’s get nuts and factor the difference of two squares up there in the numerator:

$\dfrac{(1+ \cos A)(1- \cos A)}{1- \cos A}$

Of course, you can simplify that to just $1+\cos A$

PWN Test Prep