if cos a = ¾, then the value of 16 cos^2(a/2) – 32 sin(a/2) sin (5a/2) is

Hello student, Please find the answer to your question below

use cos a = 1 – 2 sin^a/2
Form here find sin a/2
now 6 cos^2(a/2) – 32 sin(a/2) sin (5a/2)
= 6 [1 – sin^a/2 ] – 32 sin(a/2) sin (5a/2)

Now put the value of sin a/2 in above