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Math Help - Proof in a triangle.

  1. #1
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    Proof in a triangle.

    Proof AB=3.6sin0.2

    i've done.

    \frac{a}{sin0.4} = \frac{1.8}{sin1.37}

    \rightarrow a=\frac{1.8sin0.4}{sin1.37}

    but duno how to derive the answer.


    thanks!
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  2. #2
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    Quote Originally Posted by BabyMilo View Post
    Proof AB=3.6sin0.2

    i've done.

    \frac{a}{sin0.4} = \frac{1.8}{sin1.37}

    \rightarrow a=\frac{1.8sin0.4}{sin1.37}

    but duno how to derive the answer.


    thanks!
    Use the cosine rule instead.
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  3. #3
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    Quote Originally Posted by Prove It View Post
    Use the cosine rule instead.
    Still I dont understand how i would dervie the required.

    a=\sqrt{2*1.8^2-2*1.8*1.8cos0.4}

    They are not whole numbers so how would i find the required. and since this is in cos.

    thanks!
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  4. #4
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    Is it just,

    a=\sqrt{2*1.8^2-2*1.8*1.8cos0.4}
    a=\sqrt{2*3.24-3.6*1.8(0.921)}
    a=\sqrt{2*3.24-3.6*1.65}

    Or is there something I'm not getting D:
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  5. #5
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    Quote Originally Posted by BabyMilo View Post
    Proof AB=3.6sin0.2

    i've done.

    \frac{a}{sin0.4} = \frac{1.8}{sin1.37}

    \rightarrow a=\frac{1.8sin0.4}{sin1.37}

    but duno how to derive the answer.


    thanks!
    Solve it nevermind.

    cut the triangle into half.

    so it's 1.8sin0.2 x 2
    =3.6sin0.2 as required.

    haha.
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