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Homework Help: Dot product

  1. Mar 15, 2013 #1
    Find 2 unit vectors that make a 60 degree angle with <3,4>

    Vector <a,b>
    Taking b=1 cos60=1/2

    3a+4=(5/2 )sqrt(a^2+1)

    (sqrt(11)a+48)^2= 2265
    +- a=(sqrt(2265)-48)/sqrt(11)
  2. jcsd
  3. Mar 15, 2013 #2


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    Homework Helper

    I don't see a question here.

    But let me preempt it with a question of my own. You're asked to find unit vectors. Can you think of another condition you can impose on a and b to meet this requirement?

    It's fine to do it the way you did (letting b = 1), but then you still have to find unit vectors in those directions. More work.
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