9.6Secants, Tangents, and Angle Measures
Quick Answer
Angle formed by two chords inside a circle = ½(sum of intercepted arcs). Angle formed by two secants, two tangents, or a secant and tangent from an external point = ½(difference of intercepted arcs).
Essential Question
How does the location of the vertex — inside the circle, on the circle, or outside the circle — determine which arc formula to use for the angle?
Learning Goals
- 1Apply the Chord-Chord Angle Theorem (vertex inside).
- 2Apply the Secant-Secant Angle Theorem (vertex outside).
- 3Apply the Secant-Tangent Angle Theorem (vertex outside).
- 4Identify which formula to use based on vertex location.
Key Vocabulary
Chord-Chord Angle
Angle = ½(sum of intercepted arcs); vertex inside the circle.
Secant-Secant Angle
Angle = ½(difference of intercepted arcs); vertex outside 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.