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