A tangent is a straight line that touches a curve at only one point and is perpendicular to the radius at that point.
Theorem 12-1, also known as the Tangents Theorem or the Tangent-Chord Theorem, states that if a line is tangent to a circle, then it is perpendicular to the radius drawn to the point of tangency. In simpler terms, if a line touches a circle at one point, it is perpendicular to the radius that connects the center of the circle to that point of tangency.
