Tangent to a Circle Property
Line BC is a tangent line to Circle A since it intersects the circle in exactly one point. Notice the angle measure between the radius and the tangent is 90 degrees, a right angle.
Drag point B around the circle. What happens to the angle measure between the radius and the tangent line? What conjecture (rule) can you make about the angle between a radius of a circle and the tangent intersecting the radius?