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Math Help - Prove that

  1. #1
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    Unhappy Prove that

    c(acosB-bcosA)=a^2-b^2
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  2. #2
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    Quote Originally Posted by matsci0000 View Post
    c(acosB-bcosA)=a^2-b^2
    Can we have the rest of the question please, is this a triangle with sides a,b,c and angles opposite the sides A, B, C?

    Try the difference of the cosine rule for a and b.

    CB
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  3. #3
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    Quote Originally Posted by matsci0000 View Post
    c(acosB-bcosA)=a^2-b^2
    According to cosine rule
    a^2 = b^2 + c^2 - 2bc*cosA.
    From this find bc*cosA. Similarly find ac*coaB, And find the difference.
    Or, by using projection rule write c as
    c = acosB + bcosA and simplify.
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