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Dot Product of Equilateral Triangle

  1. Jun 2, 2014 #1
    1. The problem statement, all variables and given/known data

    In an equilateral triangle with sides u, v, w, where they are all unit vectors, find u dot w.

    2. Relevant equations

    u dot w = |u||w|cosθ
    3. The attempt at a solution

    The answer is ##\frac {-1} {2} ##

    cos(120) = -1/2

    Elsewhere, I read the statement that since these are already unit vectors then the dot products are simply the angles between them. What does this mean? Does something cancel out the |u||w| in the denominator? Or do |u||w| function to make the dot in terms of unit vectors so they would both be 1 in this case?

    Nevermind, got it.
     
    Last edited: Jun 2, 2014
  2. jcsd
  3. Jun 2, 2014 #2

    benorin

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    Homework Helper

    ...the dot products are the cosine of the angle between them.
     
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