Here is the question word for word:

Given that sinA = 7/25, and cosB = 9/41 and neither P(A) nor P(B) are in quadrant 1, find:

(a) sin(A+B)

I know that my first step in order to do this is solve for the unknowns in order to use an identity to answer the question. When I do this, I get cosA = 24/25 and sinB = 40/41. I have no problem with this step.

It is when I look in my answer key and see that cosA = - 24/25 and sinB = -40/41 that I am confused: why are they negative?

Here's what I already know:

- Cosine is postive in quadrants 1 & 4
- Sin is postive in quadrants 1 & 2
- Tan is postive in quadrants 1 & 3
- Neither point A or point B are in quadrant 1

Still, I don't understand why its negative, I'm having a brain block here.