Help with trigonometry?

Question

Solve 

8 sinx cosx(1-2 cos^2 x) if x = 7π /24

Answer 1

8 sin x cos x(1-2 cos^2 x) if x = 7π /24

= 4 sin 2x (1-(1+cos 2x))= -4 sin 2x cos 2x

= - 2 sin 4x = -2 sin (7pi/6)= -2 sin (pi+pi/6)= 2 sin pi/6

= 2 sin 30 = 2*1/2=1

= 4 sin 7pi/12 + 2 sin pi/6

Answer 2

= 1