Apply the trigonometric identity: $\cos\left(\theta \right)^n\sec\left(\theta \right)^m$$=\cos\left(\theta \right)^{\left(n-m\right)}$, where $x=y$, $m=3$ and $n=4$

Apply the integral of the cosine function: $\int\cos(x)dx=\sin(x)$

As the integral that we are solving is an indefinite integral, when we finish integrating we must add the constant of integration $C$