Step 1: Use identity:
\[
\sin^2x=\frac{1-\cos2x}{2}
\]
Step 2:
\[
\int\sin^2x\,dx
=
\int\frac{1-\cos2x}{2}\,dx
\]
Step 3:
\[
=\frac{1}{2}\int 1\,dx-\frac{1}{2}\int\cos2x\,dx
\]
Step 4:
\[
=\frac{x}{2}-\frac{1}{2}\cdot \frac{\sin2x}{2}+c
\]
\[
=\frac{x}{2}-\frac{\sin2x}{4}+c
\]
\[
\boxed{\frac{x}{2}-\frac{\sin2x}{4}+c}
\]