mω2y2 (Here, a= amplitude and y= displacement) when, K. E = P. E ⇒
1
2
mω2(a2−y2)=
1
2
mω2y2 ⇒a2‌=2y2 or y=±
a
√2
So, assertion (A) is correct. And P.E is maximum when y=a or particle is at extreme displacement position. Hence, reason (R) is correct but it does not explain (A).