Posted by Anonymous on .
cos A = 4/5 for angle A in Quadrant II, find sin 2A

trig 
Damon,
in Q2 sine is negative
sin^2 + cos^2 = 1
sin^2 = 1  16/25 = 9/25
sin = +/ 3/5
so sin A = 3/5
sin 2A = 2 sin A cos A
=2 (3/5)(4/5) = 24/25