9.5Tangents to Circles
Quick Answer
A tangent is perpendicular to the radius at the point of tangency. Two tangent segments from an external point are congruent. A tangent-chord angle equals half the intercepted arc.
Essential Question
How does the perpendicularity of a tangent and radius lead to the two-tangent theorem and the tangent-chord angle theorem?
Learning Goals
- 1State the Tangent-Radius Theorem.
- 2Apply the Two-Tangent Theorem.
- 3Apply the Tangent-Chord Angle Theorem.
- 4Solve problems involving tangent lines.
Key Vocabulary
Tangent-Radius Theorem
A tangent to a circle is perpendicular to the radius at the point of tangency.
Two-Tangent Theorem
Two tangent segments from the same external point are congruent.
Point of tangency
The single point where a tangent line touches the circle.
Full lesson content coming soon
Worked examples, guided practice problems, a workbook, quiz, and downloadable PDF resources will be added to this lesson in Phase 2. The learning goals and vocabulary above reflect the complete lesson scope.