MATLAB: How to differentiate a differential function with a differential variable using symbolic toolbox

symbolicSymbolic Math Toolbox

%My matlab code
syms phi(t) t
f= sin(sym(phi(t)))
% Differentiation of above equation w.r.t t
% Differentiation of above equation w.r.t diff(phi(t),t)
I'm getting error in the in the last step, when I'm trying to differentiat the f_dot equation with diff(diff(phi(t),t))
%matlab output
f_dot = cos(phi(t))*diff(phi(t), t)
Error using mupadmex
Error in MuPAD command: Invalid variable. [stdlib::diff]
Error in sym/diff (line 44)
R = mupadmex('symobj::diff', S.s, x.s, int2str(n));
Error in handle (line 7)
x=diff(f_dot,diff(phi(t), t)

Best Answer

This is not possible in MuPAD. You will need to do a change of variables. Doing a naive substitution of variables can lead to incorrect results .