The velocity of a particle in simple harmonic motion is given as
$v=\omega \sqrt{A^{2}-x^{2}}$
and magnitude of its acceleration is
$a=\omega^{2} x$
Given $|v|=|a|$
$\therefore \omega \sqrt{A^{2}-x^{2}}-\omega^{2} x$
${\omega x=\sqrt{A^{2}-x^{2}} \text { or } \omega^{2} x^{2}=A^{2}-x^{2}}$
${\omega^{2}=\frac{A^{2}-x^{2}}{x^{2}}=\frac{9-4}{4}=\frac{5}{4}}$
${\omega=\frac{\sqrt{5}}{2}}$
Time period, $T=\frac{2 \pi}{\omega}=2 \pi \cdot \frac{2}{\sqrt{5}}=\frac{4 \pi}{\sqrt{5}} \mathrm{s}$

$y = A\,\cos \,\omega t\,\cos \,2\omega t + A\,\sin \,\omega t\,\sin \,2\omega t$.
Than the nature of the function is