1. Geometry 11-4 Inscribed Angles
Inscribed angle- an angle whose vertex is on the circle.
Intercepted arc- the arc in between the sides of the angle
AC is the intercepted arc

2. Theorem 1
The inscribed angle is half the measure of the intercepted arc.
100°
50° A B C

3. Example
Find each measure.

4. Example
Find the value of a.

5. Example
Determine the value of x.
(3x – 20)° x°

6. Theorem 2
If a quadrilateral is inscribed in a circle, then its opposite angles are supplementary. A B C D

7. Example
Find the value of b.