Question

If A and B are acute angle such that SinA=8/17 and CosB=3/5.Find
1, Cos(A+B)
2, Sin(A+B)
3, Sin(A-B)

Answer 1

draw triangles to see that

cosA = 15/17
sinB = 4/5

now, use your angle sum formulas. What do you get?