9.7. Angles On and Inside a Circle http://www.ck12.org
9.7 Angles On and Inside a Circle
Here you’ll learn how to solve problems containing angles that are on or inside a circle.
What if you were given a circle with either a chord and a tangent or two chords that meet at a common point? How
could you use the measure of the arc(s) formed by those circle parts to find the measure of the angles they make on
or inside the circle? After completing this Concept, you’ll be able to apply the Chord/Tangent Angle Theorem and
the Intersecting Chords Angle Theorem to solve problems like this one.
Watch This
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/52414CK-12 Foundation: Chapter9AnglesOnandInsideaCircleA
Learn more about chords and tangents by watching the second part of the video at this link.
Follow this link to watch a video about secants.
Guidance
When an angle is on a circle, the vertex is on the circumference of the circle. One type of angleona circle is one
formed by a tangent and a chord.
Investigation: The Measure of an Angle formed by a Tangent and a Chord
Tools Needed: pencil, paper, ruler, compass, protractor
- Draw
⊙
Awith chordBCand tangent line
←→
EDwith point of tangencyC.- Draw in central angle^6 CAB. Then, using your protractor, findm^6 CABandm^6 BCE.