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Simple trigonometry check

  1. Nov 5, 2009 #1
    1. The problem statement, all variables and given/known data
    a = 1/sqrt(29) * (-2*sint, 0, -2*cost)
    length of a is?

    2. Relevant equations

    3. The attempt at a solution
    ignoring 0, we have sqrt{[(-2*sint)/sqrt(29)]^2 + [(-2*cost)/sqrt(29)]^2}. I get 2/sqrt(29) but answer is [2*sqrt(2)]/sqrt(29). Can anyone do this step by step and show me please..
  2. jcsd
  3. Nov 5, 2009 #2


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    Science Advisor

    No need to. You answer is correct. [itex]2\sqrt{2}/\sqrt{29}[/itex] would be [itex]\sqrt{4+ 4}/\sqrt{29}[/itex] but [itex]4sin^2(t)+ 4cos^2(t)= 4[/itex] not 4+ 4.
  4. Nov 5, 2009 #3
    hmm so solution must be wrong.. I wonder why no one pointed it out tho
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