i have the following equation :

R = y \[Function] 
     Piecewise[{{1.31446 Tan[1.58986 y] + 0.91209 y, 
        Abs[y] < 0.84136}, {1./(sign[y] - y), 
        0.841360 <= Abs[y] < 1.}}]];

how can i override the derivative of the function to be (R'[y_]:=) :

1./(1./R[y]^2 - 1./Sinh[R[y]]^2)
  • $\begingroup$ How about defining it as a new function (say rd1[y_]=1./(1./R[y]^2 - 1./Sinh[R[y]]^2)) and using it in your expression instead of R'[y]? $\endgroup$ – Sumit Jan 3 '18 at 11:36
  • $\begingroup$ i know that it is possible with defining another function i just wanted to ask out of curiosity if it is possible to override the derivative with the same function ? $\endgroup$ – user49047 Jan 3 '18 at 11:40
  • 1
    $\begingroup$ You can define the derivative (see here) without defining the function. But once you define the function it would be overridden. $\endgroup$ – Sumit Jan 3 '18 at 11:53

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