Integral cos 3 x cos x dx untuk di kumpul hari senin.

Materi Integral

int (cos 3x cos x dx)
= 1/2 int (2 cos 3x cos x dx)
= 1/2 int (cos 4x + cos 2x) dx
= 1/2 (1/4 sin 4x + 1/2 sin 2x) + C
= 1/8 sin 4x + 1/4 sin 2x + C

Integral Fungsi Trigonometri.

∫ cos 3x cos x dx
= ∫ 1/2 [cos (3x + x) + cos (3x - x)]
= 1/2 ∫ cos 4x + cos 2x dx
= 1/2 (1/4 sin 4x + 1/2 sin 2x) + C
= 1/2 [1/4 (2 sin 2x cos 2x) + 1/2 (2 sin x cos x)] + C
= 1/4 (2 sin x cos x) (cos 2x) + 1/2 (sin x cos x) + C
= (1/2 sin x cos x) (cos 2x + 1) + C
= (1/2 sin x cos x) (2 cos² x - 1 + 1) + C
= cos³ x sin x + C