$=-A \omega \sin \left(\omega t+\frac{\pi}{4}\right)$
For maximum speed,
$\sin \left(\omega t+\frac{\pi}{4}\right)=1 \Rightarrow \omega t+\frac{\pi}{4}=\frac{\pi}{2}$
or $\omega t=\frac{\pi}{2}-\frac{\pi}{4} \Rightarrow t=\frac{\pi}{4 \omega}$
$x = a\,\sin \,\left( {\omega t + \pi /6} \right)$
After the elapse of what fraction of the time period the velocity of the particle will be equal to half of its maximum velocity?