Permalink Submitted by Anonymous on September 17, 2015

Superimpose the graphs of y = sin(πx/n) for n = 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13... on a single pair of axes.
These curves intersect the x-axis when x = kn
and intersections which belong to only one curve correspond to prime values of n.

## An alternative graphical method

Superimpose the graphs of y = sin(πx/n) for n = 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13... on a single pair of axes.

These curves intersect the x-axis when x = kn

and intersections which belong to only one curve correspond to prime values of n.