$\boldsymbol{v}=A \omega \cos (\omega t+b)$
$a=-A \omega^{2} \sin (\omega t+b)$
so $x^{2}+v^{2} / \omega^{2}=A^{2} \ldots$ ellipse
$\boldsymbol{a}=-\boldsymbol{\omega}^{2} \boldsymbol{x} \ldots \ldots$ straight line
$v^{2}+a^{2} / \omega^{2}=A^{2} \omega^{2} \ldots . .$ ellipse