Simple Harmonic Motion

Two particles \(\mathrm{P}\) and \(\mathrm{Q}\) performs S.H.M. of same amplitude and frequency along the same straight line. At a particular instant, maximum distance between two particles is \(\sqrt{2}\) a. The initial phase difference between them is

\(\left[\sin ^{-1}\left(\frac{1}{\sqrt{2}}\right)=\cos ^{-1}\left(\frac{1}{\sqrt{2}}\right)=\frac{\pi}{4}\right]\)