Figure $a$ is a partial graph of the position function $x(t)$ for a simple harmonic oscillator with an angular frequency of $1\mathrm{.}50ra\frac{d}{s}$; figure $b$ is a partial graph of the corresponding velocity function $v(t).$ The vertical axis scales are set by $x_s=2\mathrm{.}00cm$ and $v_s=2\mathrm{.}00c\frac{m}{s}.$ What is the phase constant $($from $-$ to $rad)$ of the SHM if the position function $x(t)$ is given the form $x=x_{m}cos(t+)?$