Phase Constant: Understanding SHM & Velocity

[exparrot]

I have no question in particular I need help solving but would just like to understand what the heck is a phase constant? I keep on reading different things in Wikipedia, my textbook, Cramster... I'm just not quite sure what it is exactly and how to find it in a SHM problem. I read in my textbook that it has to do with the velocity at a specified time and the position of the particle or object at that time. I'm shown in an example problem to find φ I have to solve v(0)/x(0), but why... is not clear to me. Would appreciate help understanding this seemingly elusive constant.

 

[rl.bhat]

The general expression of SHM is x = A*sin(ωt + φ). The starting point of the particle which executes SHM, from the mean position may any where between 0 to A. The angular position of this starting point is called the phase. You can find this angle by putting t = 0 in the equation of SHM.