Evaluate the integral.

${\displaystyle \underset{\phantom{}}{\overset{\phantom{}}{}}}se{c}^{3}3xdx$

$\frac{1}{6}sec3xtan3x+\frac{1}{6}ln|sec3x+tan3x|+C$

$\frac{1}{6}se{c}^{2}3xtan3x+\frac{1}{6}ln|sec3x+tan3x|+C$

$\frac{1}{2}sec3xtan3x-\frac{1}{2}ln|sec3x+tan3x|+C$

$\frac{1}{6}sec3xtan3x+\frac{x}{6}+C$