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Homework Help: :trigonometric identity question

  1. Jan 12, 2010 #1
    URGENT:trigonometric identity question

    1. The problem statement, all variables and given/known data
    tan2x+cos2x+sin2x=sec2x
    *the 2 stands for squared since I dont know how to make the squared symbol appear on a compter



    2. Relevant equations
    http://www.analyzemath.com/Trigonometry_2/Trigonometric_identities.html
    stuff from this website and more


    3. The attempt at a solution
    (sin2x+cos2x(cos2x)+sin2xcos2x)/cos2x

    1+cos2x+sin2xcos2x/cos2x

    1+sin2xcos2x

    any help is appreciated as I have been at this for over an hour and cant figure it out and it needs to be done soon
     
  2. jcsd
  3. Jan 12, 2010 #2

    rock.freak667

    User Avatar
    Homework Helper

  4. Jan 12, 2010 #3
    Re: URGENT:trigonometric identity question

    take note of this identities:
    tan²x=sec²x-1
    cos²x+sin²x=1
     
  5. Jan 12, 2010 #4
    Re: URGENT:trigonometric identity question

    Or you can work from "base principles" replacing sin x with opposite over hypotenuse, cos x with adjacent over hypotenuse et cetera :rolleyes:
     
  6. Jan 12, 2010 #5

    Mark44

    Staff: Mentor

    Re: URGENT:trigonometric identity question

    A better idea would be to replace tan2(x) with (sin2(x))/(cos2(x)) and sec2(x) with 1/(cos2(x)). That way all your quantities would be in terms of powers of sinx and cosx.
     
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