Question

Please help, I've been stuck on this question for hours, but I am not sure on how to answer this. Find the exact value of each of the following under the given conditions. tanA=-3/4 A lies in quadrant 2, cosB=5/8 B lies in quadrant 1.
A. sin(A+B)
B.cos(A+B)
C.sin(A-B)
D.tan(A-B)

Answer 1

Wow this is a lot. Here's how you start:

Answer 2

These are right triangles with a couple of missing sides that we will find using Pythagrean's Theorem.

Answer 3

What you're looking for are called sum and difference identities. We have all of the sides of the triangles we need, we just need formulas now. One at a time, ok?

Answer 4

Sin(A+B) sin(A)Cos(B) + cos(A)sin(B)
We have values for all of those, using the sides that we have on our triangles.