# If sinA=4/5 and cosB= -5/13, where A belongs to QI and B belongs to QIII, then find sin(A+B). How do you write the second half of the formula where cos becomes A and sin is B and how do the quadrants affect these?

##### 1 Answer

A is in QI, so

#### Explanation:

Are we being played by Socratic here? It's says this was asked 13 minutes ago in the feed but 3 years ago in the comment.

Everybody should immediately recognize the Pythagorean Triples underlying this problem: