A particle in $SHM$ is described by the displacement function$x\left(t\right)=A \cos (\omega t+\varphi ), \omega =\frac{2\pi }{T}$. If the initial $t=0$ position of the particle is $1 cm$ and its initial velocity is $\pi cm/s$ what are its amplitude and initial phase angle? The angular frequency of the particle is $\pi rad/s^2$