Phase Difference of Two Particles in SHM

[JasonV]

Two particles execute simple harmonic motion of the same amplitude and frequency along close parallel lines. They pass each other moving in opposite directions each time their displacement is half their amplitude. What is their phase difference?

 

[Shooting Star]

You haven't shown any attempt. But I'm still giving you a lot of hint. The rest is upto you.

For a particle executing shm, if x=a/2, then a/2=a*sin(wt) => sin(wt) = ½ = sin pi/6 or sin(pi-pi/6). Can you find the phase diff now?