The equation of motion of a particle of mass $1 \mathrm{g}$ is $\frac{d^{2}x}{d{t}^2}+{\mathrm{\pi }}^2\mathrm{x}=0$, where $x$ is displacement (in $\mathrm{m}$) from mean position. The frequency of oscillation (in $\mathrm{Hz}$) is,

Two bodies performing S.H.M. have same amplitude and frequency. Their phases at a certain instant are as shown in the figure. The phase difference between them is

The figure shows the displacement time graph of a particle executing S.H.M. If the time period of oscillation is $2\mathrm{s}$ the equation of motion of its SHM is 

The diagram shows two oscillations. What is the phase difference between the oscillations?