Question

find integration of sin(x).sin(x)/cos(x)

Answer 1

Let's write it in a better form first ^_^:\[\int\limits_{}^{} \sin^2x/cosx dx\]

you can take:

u = sinx
du = cos x dx

so:

\[\int\limits_{}^{}u^2 du \]
\[= u^3/3 + c\]
\[= \sin^3x/3 + c\]

Hope it's clear now ^_^