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if vectors a+b+c=0 and modulus of the vectors a, b and c are 3 ,5 and 7 respectively. find the angle between the vectors a and b.

  • math -

    let the angle be Ø
    by the cosine law

    7^2 = 3^2 + 5^2 -2(3)(5)cosØ
    30cosØ = 9+25-49
    cosØ = -15/30 = -1/2
    Ø = 150°

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