If sin A= -3/5 and angle A is in quadrant IV, find cos A.

Question

I know i have to use the pythagoream identity..but i keep getting stuck.

Answer 1

sin^2 x + cos^2x = 1 do signs for quad 4

9/25 + cos^2 A = 1

cos^2 A = 16/25

cos A = 4/5 or -4/5
so +4/5 because cos is + in quadrant 4