Angles are formed by intersections of chords in the interior of a circle and angles formed in the exterior of a circle by secants and tangents. In this topic, you will learn how to determine the angle measures using given formulas.

Essential Questions

• How do you calculate the angles formed by two intersecting chords?
• How do you calculate the angles formed by intersecting secants and tangents whose vertex is outside the circle?

Warm-Up

Before you explore angles formed by intersections in the exterior and exterior of a circle, check your knowledge of vertical angles and similar triangles in this non-graded interactivity. This knowledge will help you throughout the topic. Click the player button to get started.