(c) Given, $P = \int_{0}^{3\pi}{f(\cos^{2}{x)dx}}$ …(i) and $Q = \int_{0}^{\pi}{f(\cos^{2}{x)\ dx}}$ …(ii) From Eq. (i) $P = 3\int_{0}^{\pi}{f(\cos^{2}{x)dx}}$ $\Rightarrow P = 3Q\ \Rightarrow P - 3Q = 0$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.