For the wave travelling towards left, the equations is Asin(kx + ωt). How does the same mathematical equation explain the possibility of two initial conditions. In the case of the wave travelling towards right, Asin(kx - ωt) and Asin(ωt - kx) gives two initial conditions Asin(kx) and - Asin(kx) on substituting t=0. Explaining the possibility of two different initial movements. In the case of waves travelling towards left, this difference doesn't come up. How can we explain this situation physically.