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10.3 Arcs and Chords & 10.4 Inscribed Angles

10.3 Arcs and Chords & 10.4 Inscribed Angles. Objectives. Recognize and use relationships between arcs, chords, and diameters Find measures of inscribed angles Find measures of angles of inscribed polygons. S. R. B. A. Arcs and Chords.

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10.3 Arcs and Chords & 10.4 Inscribed Angles

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  1. 10.3 Arcs and Chords & 10.4 Inscribed Angles

  2. Objectives • Recognize and use relationships between arcs, chords, and diameters • Find measures of inscribed angles • Find measures of angles of inscribed polygons

  3. S R B A Arcs and Chords • Theorem 10.2:In a or  s, two minor arcs are  iff their corresponding chords are .

  4. Diameters and Chords • Theorem 10.3:In a , if a diameter (or radius) is ┴ to a chord, then it bisects the chord and its arc. If JK ┴ LM, then MO  LO and arc LK  arc MK.

  5. More about Chords • Theorem 10.4:In a or in  s, two chords are  iff they are equidistant from the center.

  6. A C B Inscribed Angles • An inscribed angle is an angle that has its vertex on the circle and its sides are chords of the circle.

  7. A C B Inscribed Angles • Theorem 10.5 (Inscribed Angle Theorem):The measure of an inscribed angle equals ½ the measure of its intercepted arc (or the measure of the intercepted arc is twice the measure of the inscribed angle). mACB = ½m or 2 mACB =

  8. In and Find the measures of the numbered angles. Example 1:

  9. First determine Example 1: Arc Addition Theorem Simplify. Subtract 168 from each side. Divide each side by 2.

  10. So, m Example 1:

  11. Answer: Example 1:

  12. In and Find the measures of the numbered angles. Answer: Your Turn:

  13. Inscribed Angles • Theorem 10.6:If two inscribed s intercept  arcs or the same arc, then the s are . mDAC  mCBD

  14. Given: Prove: Example 2:

  15. Proof: Statements Reasons 1. 1. Given 2. If 2 chords are , corr. minor arcs are . 2. 3. Definition of intercepted arc 3. 4. 4. Inscribed angles of arcs are . 5. 5. Right angles are congruent 6. 6. AAS Example 2:

  16. Given: Prove: Your Turn:

  17. Proof: Statements Reasons 1. 2. 3. 4. 5. 1. Given 2. Inscribed angles of arcs are . 3. Vertical angles are congruent. 4. Radii of a circle are congruent. 5. ASA Your Turn:

  18. o Angles of Inscribed Polygons • Theorem 10.7:If an inscribed  intercepts a semicircle, then the  is a right . i.e. If AC is a diameter of , then the mABC = 90°.

  19. A B O D C Angles of Inscribed Polygons • Theorem 10.8:If a quadrilateral is inscribed in a , then its opposite s are supplementary. i.e. Quadrilateral ABCD is inscribed in O, thus A and C are supplementary and B and D are supplementary.

  20. ALGEBRATriangles TVU and TSU are inscribed in with Find the measure of each numbered angle if and Example 3:

  21. are right triangles. since they intercept congruent arcs. Then the third angles of the triangles are also congruent, so . Example 3: Angle Sum Theorem Simplify. Subtract 105 from each side. Divide each side by 3.

  22. Use the value of x to find the measures of Answer: Example 3: Given Given

  23. ALGEBRATriangles MNO and MPO are inscribed in with Find the measure of each numbered angle if and Answer: Your Turn:

  24. Quadrilateral QRST is inscribed in If and find and Draw a sketch of this situation. Example 4:

  25. To find we need to know To find first find Example 4: Inscribed Angle Theorem Sum of angles in circle=360 Subtract 174 from each side.

  26. To find we need to know but first we must find Example 4: Inscribed Angle Theorem Substitution Divide each side by 2. Inscribed Angle Theorem

  27. Answer: Example 4: Sum of angles in circle=360 Subtract 204 from each side. Inscribed Angle Theorem Divide each side by 2.

  28. Quadrilateral BCDE is inscribed in If and find and Answer: Your Turn:

  29. Assignment • GeometryPg. 540 #11 – 29 Pg. 549 #8 – 10, 13 – 16, 18, 22 - 25 • Pre-AP Geometry Pg. 540 #11 – 33 Pg. 549 #8 – 10, 13 – 30

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