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Math Help - Circles

  1. #1
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    Circles



    I need help with my homework. My teacher's going to grade this and then this is our study sheet.
    I had to scan the questions, since I couldn't draw it in paint.

    Can someone please explain how to figure these out?
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  2. #2
    Forum Admin topsquark's Avatar
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    What is the dot on the line in #4. Is that line supposed to be a diameter?

    -Dan
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    Yes... ............
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  4. #4
    Forum Admin topsquark's Avatar
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    Quote Originally Posted by melquan23 View Post
    Yes... ............
    Then you can finish this.

    The formula you are looking for is that an angle whose vertex is on a circle that measures an arc has a measure of half the arc.

    So the angle on the lower right measures an arc of 89 degrees, thus the angle is (1/2)*89 = 44.5 degrees.

    The angle at the top of the triangle measures an arc of 180 degrees (since the chord it intesects is a diameter it measures half the circle) so the angle is (1/2)*180 = 90 degrees.

    So your triangle has three angles: x, 44.5 degrees, and 90 degrees. The sum of the interior angles of a triangle has 180 degrees, so x = 180 - 44.5 - 90 = 45.5 degrees.

    -Dan
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