# Beautiful integral

**Calculus**Level 3

\[ \large \cos(x) \sqrt{\sec^3(2x)} \]

Which of the following is the antiderivative of the function above? Ignore arbitrary constant.

\( A: \sqrt{\frac{\sec(2x)-1}{2}} \)

\( B: \sqrt{\frac{\sec(2x)+ 1}{2}} \)

\( C: \sqrt{\frac{\sec(2x)+ 2}{2}} \)

\( D: \sqrt{\frac{\sec(2x)}{2}} \)