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Homework Help: Question on proving an identity

  1. Mar 7, 2010 #1
    So I'm given a problem in which I have to prove an identity. It goes:

    I did the problem myself and could only get to 2csc2x=2\(sin2x)= 2\(2sinxcosx). I had no idea how to get further with the problem so I looked at the answer in the back of my pre-calculus book. It said that:

    2\(2sinxcosx) = 1\(sin^2x) multiplied by sinx\cosx = csc^2xtanx

    I don't understand the part that says 2\(2sinxcosx)= 1\(sin^2x) multiplied by sinx/cosx. Could someone please explain to me how 2\(2sinxcosx) equals that?
    Last edited: Mar 7, 2010
  2. jcsd
  3. Mar 7, 2010 #2


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    Homework Helper

    Hi Lazz72, welcome to PF.
    2csc(2x) = 2/sin(2x) = 2/2six*cosx = 1/sinx*cos* = sinx/sinx*sinx*cosx = tanx/sin^2(x)
  4. Mar 7, 2010 #3
    Ahh okay I understand it now, thanks!
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