 
 
 
derive (or diff or grad) takes two arguments : an 
expression F of n real variables and a vector of these variable names.
derive returns the gradient of F,
where the gradient is the vector of all partial derivatives,
for example in dimension n=3
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Example 
Find the gradient of F(x,y,z)=2x2y−xz3.
Input :
^2*y-x*z^3,[x,y,z])or :
^2*y-x*z^3,[x,y,z])or :
^2*y-x*z^3,[x,y,z])Output :
^3,2*x^2,-(x*3*z^2)]Output after simplification with normal(ans()) :
^3,2*x^2,-(3*x*z^2)]To find the critical points of F(x,y,z)=2x2y−xz3, input :
^2*y-x*z^3,[x,y,z]),[x,y,z])Output :
 
 
