t = 0 (slider from -5 to 5, step 0.01)
dx = 1 (slider from -5 to 5, step 0.01)
S1(x) = 0.7 * sin(0.45 * π * x - 1.3 * π * t)
S2(x) = 0.7 * sin(0.45 * π * (x + dx) + 1.3 * π * t)
S(x) = S1(x) + S2(x)