Question

Jika y=2 cos 3x cos x maka dy/dx= ?

Answer 1

Y = 2 cos 3x cos x
y = cos (3x+x) + cos (3x-x)
y = cos 4x + cos 2x
dy/dx = - 4 sin 4x - 2 sin 2x
atau
dy/dx = - 4 ( 2 sin 2x cos 2x) - 2 sin 2x
dy/dx = -8 sin 2x cos 2x - 2 sin 2x
dy/dx = -2 sin 2x ( 4 cos 2x + 1)