that of the standing wave corresponding to the fourth harmonic shown in Figure 6.2.
As time increases the resultant standing wave evolves as shown in Figure 6.3. Any
point on the standing wave is described by Equation (6.22), i.e. y = A sin kx cos ωt.
The transverse displacement of every point on the standing wave varies with SHM
as cos ωt and the amplitude of this motion varies as A sin kx, i.e. the nodes and
antinodes occur at fixed points on the x-axis, cf. discussion of Equation (6.1).