Solution:
The body is in the left position at maximal compression, with an initial phase of $3 \pi / 2$ rad.
Then,
$x=a \sin (\omega t+3 \pi / 2)$
$=-a \cos \omega t$
$=-2 \cos 20 t$
As a result,
The amplitude and frequency of the functions are identical. In the beginning, they are different.