Let sin a=3/5, with a in Quadrant II, and let cos B=5/13, with B in Quadrant IV. Find the exact values for each of the following. a) sin (a+B) b) cos (a-B) c) tan 2a d) sin B/2

Answer 1

There are 2 right triangles involved: one is 3-4-5 and the other is 5-12-13.

Compute the other trig functions, but be careful about the signs!!!!

Then use the trig addition formulae to get the first 3 answers....but watch the signs, e.g. the quadrant in which a+B will be.

Use the half-angle formula for the last one...but again watch the sign!