(c) $x = 4(\cos{\pi t + \sin{\pi t)}}$ $= \frac{4}{\sqrt{2}} \times \sqrt{2}\left\lbrack \cos{\pi t} + \sin{\pi t} \right\rbrack$ $x = 4\sqrt{2}\sin{\lbrack\pi t + \frac{\pi}{4}}\rbrack\ $ So, amplitude=$4\sqrt{2}$
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.