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Math Help - Area of triangle...check work please

  1. #1
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    Area of triangle...check work please

    I have been having a hard time with these...could someone please look over my work...I was very confused on how to solve number 4, I am still attempting it as of right now....maybe someone could help me with that one....

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    Forum Admin topsquark's Avatar
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    Quote Originally Posted by aikenfan View Post
    I have been having a hard time with these...could someone please look over my work...I was very confused on how to solve number 4, I am still attempting it as of right now....maybe someone could help me with that one....

    I haven't actually checked the work, but it looks like you have applied the equations correctly.

    For the fourth one, use the Law of Cosines:
    a^2 = b^2 + c^2 - 2bc \cdot cos(A)

    The other two forms are
    b^2 = a^2 + c^2 - 2ac \cdot cos(B)

    c^2 = a^2 + b^2 - 2ab \cdot cos(C)

    As you might have guessed, these are generalizations of the Pythagorean Theorem to triangles with arbitrary angles (not just right angles.)

    -Dan
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    How do I use that formula if I do not have A? I am a little bit confused...
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    Forum Admin topsquark's Avatar
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    Quote Originally Posted by aikenfan View Post
    How do I use that formula if I do not have A? I am a little bit confused...
    b = 13, c = 11, A = 31 degrees.

    a^2 = b^2 + c^2 - 2bc \cdot cos(A)

    You aren't missing anything.

    -Dan
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