2D curve: derivative
Introduction
The user can represent the result of derivatives calculated from functions of spatial quantities or input/output parameters in the form of curves.
Operation
The curves of derivatives are created as follows:
Stage  Description 

1  The Derivative of a 2D curve command is applied to an elementary curve or a set of elementary curves of the 2D curve entity. 
2  The function representing the derivative of each analyzed curve is constructed by the calculation of the derivative at each point of the interval of the curve definition. 
3  The new elementary curves are added to the already available curves of the 2D curve entity. 
Principle
The derivative is calculated starting from the function represented by the analyzed curve. The backward derivative principle is used.
Given a curve representing the function f(x), the calculation of the derivative in each point is carried out as follows:
The number of points of the curve representing the derivative is the same as that of the initial curve minus 1.
Thus:
The 1st abscissa of the curve representing the derivative corresponds to the 2^{nd} abscissa of the initial curve; the 2^{nd} abscissa of the curve representing the derivative corresponds to the 3^{rd} abscissa of the initial curve, etc.
The abscissa values must be strictly increasing ones (b>a).
Backward derivative: reminder
The backward derivative of the function f in is equal to:
Calculate the derivative of a 2D curve
To calculate (and plot) the derivative of a 2D curve, follow instructions below:
Step  Action 

1 
In the menu :

→  A selection box opens 
2 
In the selection dialog:

3 
In the Derivative of a 2D curve dialog:

→  The curves of the derivative are calculated and displayed in the 2D curve sheet. 