Asked by Anonymous

How does ∫ sin(x)/cos(x)dx become sin(x)+C? Why did cos(x) disapear?
Answered by typo
it is ∫ cos(x)/sin(x)dx not ∫ sin(x)/cos(x)dx.
Answered by Bosnian
Substitution: sin ( x ) = u , cos ( x ) dx = du

∫ cos ( x ) dx / sin ( x ) = ∫ du / u = ln | ( u ) | + C = ln | sin ( x ) | + C