Question

Find: ∫ sin x · log cos x dx

Answer 1

`∫  sin "x" ·log  cos"x"  "dx"`

Substitute cos x = t

sinx dx = dt

`∫ - "log t  dt"`

= - (t log t - t ) + C

= - t log t + t + C

= - cos x log (cos x )+ cos x + C