To see how two traveling waves of the same frequency create a standing wave. consider a traveling wave described by the formula:

y1(x, t)=asin(kx−ωt).

this function might represent the lateral displacement of a string, a local electric field, the position of the surface of a body of water, or any of a number of other physical manifestations of waves.
find ye(x) and yt(t). keep in mind that yt(t) should be a trigonometric function of unit amplitude.