Find a function describing B (on the x-axis) to the Origin

The Question at hand
Point B is a point on the x-axis that is always exactly 3 units away from point A. As Point A rotates around the circle counterclockwise, find a function defining the x-value of Point B.[br][br]Helper Line box will show the material for an animation.[br][br]Answer will show the actual answer.

Information: Find a function describing B (on the x-axis) to the Origin