⇒ x2=2Rx‌cosec‌θ+L2−R2 displacement of S.H. M. is in the form of x=A‌sin‌ω‌t+c Therefore it is not S. H. M. It is S. H. M. only which. It L = R. ⇒ x2=2Rx‌cos‌θ ⇒ x=2R‌cos‌θ x = 2R cos ωt [ S.H. M.] But period of this motion is T