Question

A line that intersects a circle exactly once is called a tangent. What is the relationship of a tangent to a circle? To investigate this question, carefully copy the diagram showing line l tangent to •C at right onto tracing paper. Fold the tracing paper so that the crease is perpendicular to line l through point P. Your crease should pass through point C. What does this tell you about the tangent line?

Answer 1

Tangent lines only have one point of contact with the circumference of the circle.

There is only one tangent line per point and its geometrical relation to the circle is that it is perpendicular to the radius, expressed as the segment between the center C and the point P where the tangent touches the circle.

We can see it in the picture as: