12-1 Tangent Lines
Objective
To use properties of a tangent to a circle
Lesson Vocabulary
- tangent to a circle
- point of tangency
In the Solve It, you drew lines that touch a circle at only one point. These lines are called tangents. This use of the word tangent is related to, but different from, the tangent ratio in right triangles that you studied in Chapter 8.
Essential Understanding A radius of a circle and the tangent that intersects the endpoint of the radius on the circle have a special relationship.
Take Note Theorem 12-1
Theorem
If a line is tangent to a circle, then the line is perpendicular to the radius at the point of tangency.
If …
Then …
Table of Contents
- 6-1 The Polygon Angle-Sum Theorems
- 6-2 Properties of Parallelograms
- 6-3 Proving That a Quadrilateral Is a Parallelogram
- 6-4 Properties of Rhombuses, Rectangles, and Squares
- 6-5 Conditions for Rhombuses, Rectangles, and Squares
- 6-6 Trapezoids and Kites
- 6-7 Polygons in the Coordinate Plane
- 6-8 and 6-9 Coordinate Geometry and Coordinate Proofs