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Ti-84 strange derrivative problem

  1. Jun 10, 2012 #1
    Hey there, I'm using a Ti-84 calculator to calculate derrivatives.
    It goes like this:

    Y1={the actual function}
    Y2=nDeriv(Y1,X,X)

    This seems to work, except for functions with cos(x), sin(x),..

    Example:
    Y1=X²
    Y2=nDeriv(Y1,X,X)
    Y3=2X

    As Y3 represents the actual derrivative of Y1, Y2 and Y3 are the same.
    But when I enter the following:

    Y1=sin(X)
    Y2=nDeriv(Y1,X,X)
    Y3=cos(x)

    As cos(x) is the derrivative of sin(x), Y2 and Y3 should be the same. But they aren't.
    For X=3, I get:
    Y1=0.258819045103
    Y2=0.016858586
    Y3=0.965925826289

    Does anyone have an idea what I'm doing wrong? Thanks in advance.

    E: I think I found the solution myself. It seems that X was considered as a degree value instead of a radian value!
     
    Last edited: Jun 10, 2012
  2. jcsd
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