If sin theta is 8÷17;cos beta is 9÷41 where theta is obtuse and beta is acute. Find sin(theta + beta)

Answer 1

We have angle a in QII, and angle b in QI. So,

sin a = 8/17
cos a = -15/17

sin b = 40/41
cos b = 9/41

sin(a+b) = sin a * cos b + cos a * sin b
= (8/17)(9/41)+(-15/17)(40/41) = -528/697