Find each value if cos A=12/13 with 0 (degrees) <= A <= 90 (degrees) and if sin B=8/17 with 90 (degrees) <= B <=180 (degrees)

Question

1. sin(A+B)
2. cos(A-B)
3. tan(A-B)

Answer 1

draw the two triangles in standard position.
A is a 5-12-13 triangle, and B is 8-15-17.

sinA = 5/13
cosA = 12/13
tanA = 5/12

sinB = 8/17
cosB = -15/17
tanB = -8/15

Now just plug those values into your addition formulas for the trig functions.