Particle paths and standing waves

Question

Here $x_0$ is the $x$ coordinate of a point in $x-y$ space

Here $x_0$ is the $x$ coordinate of a point in $x-y$ space.

I understand where the nodes and crests are on the figure. However, I don't understand why under the crests $cos(k x_0)=0$ . I don't really understand what is meant by 'under' here. I take it 'under' does not mean below as that would contradict the figure

Answer 1

That statement is for non-standing waves. Line two describes the figure, which features standing waves.