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Sin(t) - cos(t) can be rewritten as?

  1. Feb 27, 2009 #1
    The problem:

    sin(t) - cos(t) can be rewritten as ? - The answer is sqrt(2)cos(3PI/4 - t).

    there is an equation Re^(xt)cos(bt - angle).
    R = sqrt(A^2+B^2)

    So i get the following answer:

    sqrt(2)(cos(t - 3PI/4)).

    Why does the correct answer have the 3PI/4 switched with the t??
  2. jcsd
  3. Feb 27, 2009 #2


    User Avatar
    Science Advisor

    If you remember the graph of cosine, the property should come to mind that:
    cos(-x)=cos(x), which is what's being used here.
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