Question

Resolver las siguientes integrales

∫sen(7x)sen(3x)dx

Answer 1

Utilizamos una identidad trigonométrica.

sen(a) . sen(b) = 1/2 [cos(a - b) - cos(a + b)]

a = 7 x; b = 3 x; a - b = 4 x; a + b = 10 x

Reemplazamos:

1/2 ∫[cos(4 x) - cos(10 x)] dx =

= 1/2[1/4 sen(4 x) - 1/10 sen(10 x)]

= 1/8 sen(4 x) - 1/20 sen(10 x)

Mateo