Find each indicated measure for ⊙ O . circle dot o .

20. 1. m B C ⌢ m , modified b c with frown above
    2. m ∠ B m angle b
    3. m ∠ C m angle c
    4. m A B ⌢ m , modified eh b with frown above
    
21. 1. m ∠ A m angle eh
    2. m C E ⌢ m , modified c e with frown above
    3. m ∠ C m angle c
    4. m ∠ D m angle d
    5. m ∠ A B E m angle eh b e
    
22. Think About a Plan What kind of trapezoid can be inscribed in a circle? Justify your response.
    • Draw several diagrams to make a conjecture.
    • How can parallel lines help?

Find the value of each variable. For each circle, the dot represents the center.

23. 
24. 
25. 
    Image Long Description

Write a proof for Exercises 26 and 27.

26. Proof Inscribed Angle Theorem, Case II

    Given: ⊙ O circle dot o  with inscribed ∠ A B C angle eh b c

    Prove: m ∠ A B C = 1 2 m A C ⌢ m angle , eh b c equals . 1 half . m , modified eh c with frown above

    (Hint: Use the Inscribed Angle Theorem, Case I.)

    

27. Proof Inscribed Angle Theorem, Case III

    Given: ⊙ S circle dot s  with inscribed ∠ P Q R angle p q r

    Prove: m ∠ P Q R = 1 2 m P R ⌢ m angle , p q r equals . 1 half . m , modified p r with frown above

    (Hint: Use the Inscribed Angle Theorem, Case I.)

    

28. Television The director of a telecast wants the option of showing the same scene from three different views.
    1. Explain why cameras in the positions shown in the diagram will transmit the same scene.
    2. Reasoning Will the scenes look the same when the director views them on the control room monitors? Explain.

    

    

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