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-   -   Verify identity (sin^3(x) cos^3(x)) /sin(x) cos(x) (https://www.askmehelpdesk.com/showthread.php?t=519964)

  • Oct 24, 2010, 07:11 PM
    mrenney
    verify identity (sin^3(x) cos^3(x)) /sin(x) cos(x)
    = (csc^2(x) - cot(x) - 2cos^2(x))/1 - cot^2(x)
  • Oct 24, 2010, 09:55 PM
    Unknown008

    Post your question with the appropriate groupings making use of brackets please and avoid omitting signs. The way you gave us is this way:




    Which is not true.
  • Oct 24, 2010, 11:00 PM
    mrenney
    Comment on Unknown008's post
    Sorry I wrote the question wrong this is the correct one, verify this identity: (sin^3(x) cos^3(x)) /(sin(x) + cos(x)) = (csc^2(x) - cot(x) - 2cos^2(x)) / (1 - cot^2(x))
  • Oct 24, 2010, 11:02 PM
    mrenney
    Comment on Unknown008's post
    Sorry I wrote this question wrong again this is really the correct one, verify this identity: (sin^3(x) - cos^3(x)) / (sin(x) + cos(x)) = (csc^2(x) - cot(x) - 2cos^2(x)) / (1 - cot^2(x))
  • Oct 24, 2010, 11:46 PM
    Unknown008
    Okay.



    I think it would be easier to start with the left part:



    1. Factorise in the form .
    2. Multiply by (sin(x) - cos(x)) in both numerator and denominator.
    3. Expand and simplify numerator and denominator.
    4. Simplify with identity cos^2(x) + sin^2(x) = 1
    5. Expand numerator.
    6. Divide numerator and denominator by sin^2(x)

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