You are given that cos(A)=−4/5, with A in Quadrant II, and sin(B)=−24/25, with B in Quadrant III. Find sin(A+B). Give your answer as a fraction.

Answer 1

Draw and label a diagram! Learn to use Pythagoras!

cos A = -4/5 ⇒ sin A = 3/5 in QII

sin B = -24/25 ⇒ cos B = -7/25 in QIII

Now substitute values into appropriate formula