To find the lengths of ON and MN, we have to know the coordinates of N. Because ND is perpendicular with the base of the triangle which runs along the x-axis, N and D are on a vertical line and must have the same x-coordinate, h. We also see that N reaches a height of k units on the y-axis, so N has the y-coordinate k.
When we know the coordinates of N, we can use the Distance Formula to find the length of ON and MN.
