$v=-wAsin(wt+\varphi )=>sin(wt+\varphi )=\frac{-v}{wA}$
$a=-w^2Acos(wt+\varphi )=>cos(wt+\varphi )=\frac{-a}{w^2A}$
Co $sin^2(wt+\varphi )+cos^2(wt+\varphi )=1$
$=>\frac{v^2}{w^2.A^2}+\frac{a^2}{w^4.A^2}=1$
$<=>\frac{v^2}{w^2}+\frac{a^2}{w^4}=A^2$
Dap an $D$