Question

if tax=-4/3 and x is in quadrant 2, then cos2x=?
3/5
7/25
-7/25
-3/5

Answer 1

"tax=-4/3" ??? Please go back and check that you have copied down this expression correctly.

Answer 2

best you draw a right angled triangle and input your information with Pythagoras; theorem to find cos x (don't worry about signs yet)


Then use cos2x = 2cos^2(x) -1 and sub in cos(x) *which will be negative in Quadrant II.