# A begginners question on S.H.M

1. May 23, 2004

### creativeassault

Hello,
this is my first post on this forum and it is about simple harmonic motion. I can't seem to understand why the displacement x has two functions. What I mean is, x(t)=A.Sin(wt+phi) is the solution of differential equation of s.h.m; which is used by our physics teacher to derive the velocity and acceleration of a particle performing s.h.m; BUT in many text books I found that x(t)=A.Cos(wt+phi) ... my question is how can there be two values for x ?

Any help would be very helpfull,
Thank You.
Rohit Arondekar.

2. May 23, 2004

### arildno

Both versions are perfectly acceptable, as long as you remember that the "phi" in the sine representation will differ from the "phi" in the cosine representation, since we have, in general:
$$\cos(\theta-\frac{\pi}{2})=\sin(\theta)$$

3. May 24, 2004

### creativeassault

Yay! cheers arildno :)