GATE Chemical 2014 | Question: 3

Question

If $f*(x)$ is the complex conjugate of $f(x)=\cos(x) + i\: \sin(x)$, then for real $a$ and $b$, $\int _{a}^{b}f*\left ( x \right )f\left ( x \right )$ is $ALWAYS$

• A. positive
• B. negative
• C. real
• D. imaginary