How do I evaluate tan(x)sec3(x)dx?

1 Answer
Feb 1, 2015

I can write the integral as:
sin(x)cos(x)1cos3(x)dx=
=sin(x)cos4(x)dx=
but: d(cos(x))=sin(x)dx
and the integral becomes (multiplying and dividing by 1):
=sin(x)cos4(x)dx=
=1cos4(x)d(cos(x)=
=cos4(x)d(cos(x))=
=cos3(x)3+c=
=cos3(x)3+c