Tangent Passing Through a Fixed Point
A tangent line to a circle can only be formed if the line is perpendicular to the radius at the point of tangency. If the line is required to pass through a fixed point outside the circle, this limits the tangent lines to two as seen below. The moment segment is equal or less than the radius, no tangent lines can be formed anymore. This only happens when the fixed point is inside the circle. The slider changes the position of the point. Adjust this manually to see various scenarios.