\(12.5=25 \sin \frac{2 \pi}{3} \times t \quad\left(\because \omega=\frac{2 \pi}{\mathrm{T}}\right)\)
\(\frac{\pi}{6}=\frac{2 \pi}{3} t\)
\(t=\frac{1}{4} \sec =0.25 \mathrm{sec}\)
\(t^{\prime}=2 t\)
\(=2 \times 0.25=0.5 \mathrm{sec}\)
for either side