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Homework Help: Calculating angle between two vectors

  1. Sep 10, 2010 #1
    1. The problem statement, all variables and given/known data

    Use the definition of scalar product, a·b = ab cos θ, and the fact that a·b = axbx + ayby + azbz to calculate the angle between the two vectors given by a = 1.0 ihat + 5.0 jhat + 1.0 khat and b = 6.0 ihat + 3.0 jhat + 4.0 khat.

    2. Relevant equations

    a·b = ab cos θ

    3. The attempt at a solution

    i really dont have any clue were to start
  2. jcsd
  3. Sep 10, 2010 #2

    Andrew Mason

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    Science Advisor
    Homework Helper

    Write out the expression for [itex]\theta[/itex] in terms of the length of a x length of b and [itex]a_xb_x + a_yb_y + a_zb_z[/itex] (hint: you need the arccos function and pythagoras' theorem).

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