For $SHM$ $\frac{\mathrm{d}^{2} \mathrm{y}}{\mathrm{dt}^{2}} \propto-\mathrm{y}$

$\frac{\mathrm{dy}}{\mathrm{dt}}=2 \omega \sin \omega t \cos \omega t=\omega \sin 2 \omega t$

$\frac{d^{2} y}{d t^{2}}=2 \omega^{2} \cos 2 \omega t$ which is not proporti-

onal $to - y.$ Hence it is not in $SHM.$