Solving equations in trigonometry

Question

Determine tan(a-b), given that cos a = 3/5, sin b = 1/2 and both a and b are in the first quadrant.

Answer 1

tan a = 4/3, tan b =sqrt(3)/3...use Pythagorean theorem

and tan(a-b)=(tan-tan b)/(1+tan a tan b)