Derivative
Function 
Derivative(function)
Derivative(function, varName)

Derivative is included by default in each file as part of the Math library.
See also:
Use
The Derivative() function returns the derivative of a function. The result is given as a new function that can be used. The input for Derivative() is given as a named custom function, or as an inline function.
The resulting function is calculated symbolically, but if no symbolic solution can be found, a numerically derived function will be given.
If the input function has more than one variable, then Derivative() performs a partial derivative, where the second input specifies which variable the partial derivative will be done on. The second input must be given as a text value that matches one of the variables in the input function.
Units can be used, but care must be taken that the variables and functions work together.
Simple Examples
Derivative(x=>x^2+x+1) = 2*x + 1
Derivative((x, y)=>x^2+x*y+y^2, "x") = 2*x + y
Example using the resulting function
Example using units