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Use trig identities to show that

  1. Apr 8, 2014 #1
    1. The problem statement, all variables and given/known data
    use trig identities to show that

    (b) cos(tan^(−1)[x])=1/√(1+x^2) for −1/2π<x<1/2π.


    2. Relevant equations
    i think Pythagoras has to applied but that is geometric reasoning hmm


    3. The attempt at a solution
    1. The problem statement, all variables and given/known data



    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Apr 8, 2014 #2

    jbunniii

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    Maybe try bringing ##\sin(\tan^{-1}(x))## into the picture?
     
  4. Apr 8, 2014 #3

    Dick

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    tan^(-1)(x) represents an angle whose opposite side is x and whose adjacent side is 1. Use that geometry to figure out the cosine.
     
  5. Apr 8, 2014 #4

    SammyS

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    cos → sec → tan
     
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