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Trig Identity

  1. Aug 10, 2011 #1
    1. The problem statement, all variables and given/known data
    Prove that tanx + 1 = secx.


    2. Relevant equations
    sinx/cosx + 1 = 1/cosx


    3. The attempt at a solution
     
  2. jcsd
  3. Aug 10, 2011 #2

    NascentOxygen

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    Staff: Mentor

    Have you tried substituting a value, any value, to confirm this may be true?

    It will be rather difficult to prove that it's an identity if it really isn't. :redface:
     
  4. Aug 11, 2011 #3

    eumyang

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    Homework Helper

    Check wherever you got this problem from to see if you copied it correctly. It looks like something is missing in the original problem.
     
  5. Aug 11, 2011 #4
    Don't you mean tan2x + 1 = sec2x?
     
  6. Aug 11, 2011 #5
    I wish I did. I am reviewing precalc with a student as a private tutorto prepare him for H.S. Calc. and this problem was one that neither of us could figure out.
     
  7. Aug 11, 2011 #6
    I think you forgot the squares... if you meant them then
    start with
    sin(x)^2+cos(x)^2=1
    Do you have any clue or idea were to go from here?
     
  8. Aug 12, 2011 #7

    HallsofIvy

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    Staff Emeritus
    Science Advisor

    What people are telling you is that you cannot prove tan x+ 1= sec x, it is NOT true. For example if x= 45 degrees ([itex]\pi/4[/itex], the left side is 2 while the right side is [itex]\sqrt{2}[/itex].

    You can prove that [itex]tan^2 x+ 1= sec^2(x)[/itex] for all x.
     
  9. Aug 12, 2011 #8
    I realize that and have come to the conclusion that either I miscopied the problem, the book has a misprint, or we both misunderstood the instructions. Thanks everyone. I will look at the problem at our next session and figure out where to go.
     
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