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Homework Help: Hard C3 question

  1. Jun 4, 2008 #1

    im stuck on the top question on part B

    i can do the difference of 2 squares on the LHS but how do i get rid of the cosec²x - cot²x ??

  2. jcsd
  3. Jun 4, 2008 #2
    mis-post, oops!

    Edit: Well, as I'm here...

    [itex]cosec^2\theta - cot^2\theta = 1[/itex]
    [itex]cosec^2\theta + cot^2\theta = -1[/itex]

    Well, that's the RHS...

    [itex]-cot^4\theta = -cot^2\theta \times cot^2\theta\newline[/itex]
    [itex]= (1 - cosec^2\theta)(cosec^2\theta - 1)\newline[/itex]
    [itex]= -1 + cosec^2\theta - cosec^4\theta - cosec^2\theta\newline[/itex]

    Back to the original question!

    [itex]cosec^4\theta - cosec^4\theta - 1 = - 1\newline[/itex]
    [itex]-1 = -1[/itex]

    I think that's correct :S

    (Hmm, latex is messed up, how do I make a newline?)
    Last edited: Jun 4, 2008
  4. Jun 4, 2008 #3

    Gib Z

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    Homework Helper

    Use the result in part a) like it told you to.
  5. Jun 4, 2008 #4

    D H

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    Staff Emeritus
    Science Advisor

    3lliot, please do not give out answers. We offer free help here at PF, not free answers.
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