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    I need help answering a question:

    In triangle abc, cosA = 0.5, AB = 6cm, BC = 2x cm, AC = x cm, show that x^2 + 2x - 12 = 0
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    Hi Bethany, this question might be better in the Maths forum
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    (Original post by Bethanyt5560)
    I need help answering a question:

    In triangle abc, cosA = 0.5, AB = 6cm, BC = 2x cm, AC = x cm, show that x^2 + 2x - 12 = 0
    COSINE RULE
    You know how to use the cosine rule?
    i.e.  a^2 = b^2 + c^2 -2bc \cos A

    Draw out the triangle ABC.
    Put the lengths given in the question.

    You'll notice that 2x is opposite angle A.
    And you're given cos A.

    So start subbing the appropriate values into the cosine rule, and then reduce it to the quadratic given.
 
 
 
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