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triangle ABC, AB = x cm, BC = (x-4)cm, AC =10 cm and angle BAC = 60° calclulate the value of x

  • math -

    check out law of cosines

  • math -

    Triangle ABC
    AB = x
    BC = x - 4
    AC = 10
    angle BAC = 60 deg

    Using Law of Cosines
    a^2 = b^2 + c^2 - 2bc cos A
    (x -4)^2 = 10^2 + x^2 - 2(10)(x)cos 60
    x^2 - 8x + 16 = 100 + x^2 - 20x (0.5)
    x^2 - 8x + 16 = 100 + x^2 - 10x
    2x = 84
    x = 42

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