Question

please integrate sine^3x ???

Answer 1

\[\int\limits_{}^{}\sin (3x) \ dx\]
Perform a substitution, where
\[u = 3x \ \ du = 3 \ dx \ \ \frac{1}{3}du = 1 \ dx\]
Then you have an integral \[\frac{1}{3} \int\limits\limits_{}^{}\sin (u) \ du = -\frac{1}{3}\cos(u) + c\]
Substitute u = 3x back in and you'll have your answer
\[-\frac{1}{3}\cos(3x) + c\]