
Clearly, $0=\omega t$
Now, we can write $O R=O Q \cos (90-0)$
$=O Q \sin 0=O Q \sin \omega t$
$=r \sin \omega t|\because O Q=r|$
$\Rightarrow x=r \sin \omega t=B \sin \omega t[\because r=B]$
$B \sin \cdot \frac{2 \pi}{T} t=B \sin \left(\frac{2 \pi}{30} t\right)$
Clearly, this equation represents $SHM.$

