A plane with points distributed on a circular trajectory having   100 mm diameter and the center at the coordinate point (Xc=0, Yc=0, Zc=20) is measured using a number of given points. A probe with a 2 mm diameter sphere is used. The probing direction of the points is normal to the plane.

What is the X-coordinate of one of measurement points on the plane, being on circular trajectory, knowing that the angle between the polar radius of the point and the X-axis is equal to 30 degrees?