$|v|=|a|$
$\Rightarrow \omega \sqrt{A^{2}-x^{2}}=\omega^{2} x$
$\Rightarrow \omega=\frac{\sqrt{A^{2}-x^{2}}}{x}$
$\Rightarrow 2 \pi f=\frac{\sqrt{A^{2}-x^{2}}}{x}$
$\Rightarrow f=\frac{1}{2 \pi}\left(\frac{\sqrt{A^{2}-x^{2}}}{x}\right)=\frac{1}{2 \pi}\left(\frac{\sqrt{2^{2}-1^{2}}}{1}\right)=\frac{\sqrt{3}}{2 \pi}$

