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Thread: octagon?

  1. #1
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    octagon?

    octagon?

    PLEASE HELP


    1.What is the sum of the measures of the interior angles of a heptagon?

    A. 1260∘
    B. 2520∘
    C. 900∘
    D. 1800∘

    my answer is C

    5.If the sum of the interior angle measures of a polygon is 3600∘, how many sides does the polygon have?
    A. 22 sides
    B. 20 sides
    C. 18 sides
    D. 10 sides

    MY ANSWER ?

    3.What is the angle measure of each exterior angle of a regular octagon?
    A. 45∘
    B. 135∘
    C. 360∘
    D. 1080∘

    MY ANSWER ?
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  2. #2
    Forum Admin topsquark's Avatar
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    Re: octagon?

    How did you get your answer for 1? The rest are similar. Without knowing what you did we can't help you as well.

    -Dan
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  3. #3
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    Re: octagon?

    This is very strange. You title this "octagon" and the first word is "octagon" buy you ask about a "heptagon"?

    In any case, imagine drawing lines from some point in the middle of the polygon to each vertex. For a polygon with n sides that creates n triangles. Since the angles in a triangle total 180 degrees ($\displaystyle \pi$ radians) the n triangles have total angles of 180 n degrees ($\displaystyle n\pi$ radians. However the angles at the central point total 360 degrees [tex] ($\displaystyle 2\pi$ radians) so the measures of the angles of the polygon itself total 180n- 360 degrees ($\displaystyle n\pi- 2\pi= (n- 2)\pi$ radians). For example, when n= 3 that is of course 3(180)- 360= 180 degrees ($\displaystyle (3- 2)\pi= \pi$ radians) or when n= 4, that is 4(180)- 360= 360 degrees ($\displaystyle (4- 2)\pi= 2\pi$ radians).
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  4. #4
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    Re: octagon?

    Find the formula using George Google...
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