SBMPTN

Pertanyaan

dalam ΔABC jika AB=6 AC=8 dan tan ∠ABC=2[tex]\sqrt3 [/tex] maka tab∠BAC= ...
mohon dibantu ya kaa makasih :)

1 Jawaban

  • Tan mi = √((2√3)^2 + 1^2) = √(12 + 1) = √13
    Sin B = de/mi = (2√3)/√13

    AB/(sin C) = AC/(sin B)
    6/(sin C) = 8/(2√3/√13)
    6/(sin C) = (8√13)/(2√3)
    6/(sin C) = (4√13)/√3
    3/(sin C) = (2√13)/√3
    2√13 sin C = 3√3
    Sin C = (3√3)/(2√13) = de/mi
    sa = √((2√13)^2 - (3√3)^2) = √(52 - 27) = √25 = 5
    Tan C = de/sa = (3√3)/5

    A + B + C = 180° => A = (180° - (B + C))
    Tan <BAC
    = Tan A
    = Tan (180° - (B + C))
    = - Tan (B + C)
    = - (Tan B + Tan C)/(1 - Tan B Tan C)
    = - (2√3 + (3√3)/5) / (1 - 2√3 .(3√3)/5) . 5/5
    = - (10√3 + 3√3) / (5 - 18)
    = - (13√3) / -13
    = √3

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