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Trigonometry Question

  1. May 1, 2015 #1
    I know that ##\sin^2 x + cos^2 x = 1.##

    Is this mean that

    ##\sin^2 2x + \cos^2 2x = 1##

    or

    ##\sin^2 3x + \cos^2 3x = 1##

    or

    ##\sin^2 4x + \cos^2 4x = 1##

    and so on?
     
  2. jcsd
  3. May 1, 2015 #2
  4. May 1, 2015 #3

    Mark44

    Staff: Mentor

    ##sin^2(\text{whatever}) + cos^2(\text{whatever}) = 1##
    The "whatever" in both places has to be the same, of course.
     
  5. May 1, 2015 #4
    Does ##\sin^2 2x = \frac{1 - \cos 4x}{2}?##
     
  6. May 1, 2015 #5

    Mark44

    Staff: Mentor

    ##\sin^2(A) = \frac{1 - \cos(2A)}{2}##
    If A = 2x, what is 2A?
     
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