Question

Given that sec x = 3/5, csc y = 3 where x and y are in the first quadrant. Find the exact value of sin (x + y).

Answer 1

secx cannot be less than 1. So I assume you meant secx = 5/3.

cosx = 3/5, so sinx = 4/5
siny = 1/3, so cosy = √8/3
Now just use the fact that
sin(x+y) = sinx cosy + cosx siny