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Trig quadrant Question

  1. Nov 18, 2006 #1
    Solve: secx=-5.2, 0≤x≤2π

    I'm getting 2 answers:
    1.76, 4.52

    The answer key is telling me there is only one
    1.76

    How do I only get 1 answer from this?

    Thanks,
     
  2. jcsd
  3. Nov 18, 2006 #2
    Evaluate: cot4.47

    I'm getting .23 when i plug in: tan(1/4.47)

    but the answer key says .25
    am I doing something wrong?

    thanks
     
  4. Nov 19, 2006 #3
    1. [tex] \sec x = -5.2, \; 0\leq x\leq 2\pi [/tex]

    [tex] \frac{1}{\cos x} = - 5.2 [/tex]

    [tex] \cos x = -\frac{1}{5.2} = [/tex]

    [tex] \arccos(\cos x) = 1.76 [/tex]

    [tex] x = 1.76 [/tex]


    2. [tex] \cot 4.47 = \frac{1}{\tan 4.47}[/tex] not [tex] \tan(\frac{1}{4.47}) [/tex]
     
  5. Nov 19, 2006 #4
    thanks, I see what I did wrong for #2

    but, why doesnt #1 have 2 answers?
     
  6. Nov 20, 2006 #5
    Because the second answer is in quadrant 4, where cos is positive.
     
  7. Nov 20, 2006 #6
    No, it's in the 3rd quadrant. There should be 2 solutions.
     
  8. Nov 21, 2006 #7

    VietDao29

    User Avatar
    Homework Helper

    Yes, there should be 2 answers. Cheers. :)
     
  9. Nov 21, 2006 #8
    Alright
    Thanks everyone
     
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