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Homework Help: Angle between two vectors

  1. Jun 9, 2014 #1
    Hi Guys,

    Im working on finding an angle between two vectors.

    a [ 1,2,3 ]
    b [ 4, -1, 0]

    //a// = sqrt(1^2+2^2+3^2) = sqrt14
    //b// = sqrt(4^2+(-1)^2+0^2 = sqrt17

    Dot product
    1.4 + 2.-1 + 3.0 = 2

    cos^-1 2/ sqrt14 sqrt17
    cos^-1 (1/( ???? )

  2. jcsd
  3. Jun 9, 2014 #2


    User Avatar
    Homework Helper

    What is the problem? The cosine of the angle is ##\frac{2}{\sqrt{17}\sqrt{14}}##. Just type in to your calculator, and take 'inverse cosine' of the result.

    And next time write out the parentheses. cos^-1 2/ sqrt14 sqrt17 means cos^-1(2) * sqrt(14) *sqrt(17) which has no sense.

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