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Math Help - two adjacent triangular fields

  1. #1
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    two adjacent triangular fields



    1. Using triangle ACD calculate the length AC.
    2. Calculate the size of angle ABC

    thanks
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  2. #2
    Member pflo's Avatar
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    Quote Originally Posted by peachgal View Post


    1. Using triangle ACD calculate the length AC.
    2. Calculate the size of angle ABC
    For triangle ACD you know two sides (a and c) and the angle (D) opposite the unknown side (d), you need an equation that relates these quantities. That would be the Law of Cosines: d^2=a^2+c^2-2ac*cos(D). Note that cos(60^o)=\frac{1}{2}.

    After that, look at triangle ABC. You now know two sides (a and b), one of which is opposite your unknown angle (B) one of which is opposite a known angle (A). The equation that relates these quantities is the Law of Sines: \frac{sin(A)}{a}=\frac{sin(B)}{b}. Solve this for sin(B) (note that sin(30^o)=\frac{1}{2}), then use the inverse sine (also known as arcsin) to get angle B.
    Last edited by pflo; May 27th 2010 at 07:51 PM. Reason: latex error
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