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  • Apr 24, 2013, 11:01 PM
    nohea
    verify the identity
    (cos3x + sin3x)/(cos3x - sin3x) - (cos3x - sin3x)/(cos3x + sin3x) = 2tan6x

    help please. I'm lost. I substitute w for 3x then go from there but I get stuck at 4sinwcosw/(2cos^2w-1)
  • Apr 25, 2013, 05:57 AM
    ebaines
    Quote:

    Originally Posted by nohea
    i get stuck at 4sinwcosw/(2cos^2w-1)

    2sinwcosw/(cos^2w-sin^2w) is the formula for tan(2w):

    tan(2w) = sin(2w)/cos(2w) = 2 sin(w)cos(w)/(2cos(w)-1)

    So you're there!

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