Reference Guide

3-56 Full Command and Function Reference
See also: CLEAR, DROPN
DERIV
Type: Function
Description: Returns the partial derivatives of a function, with respect to the specified variables.
Access: Calculus, P CALCULUS or !Ö DERIV . & INTEG .
Input: Level 2/Argument 1: A function or a list of functions.
Level 1/Argument 2: A variable, or a vector of variables. The variable or variables must not exist
as variables stored in the current directory nor directories above it.
Output: The derivative, or a vector of the derivatives, of the function or functions.
Flags: Exact mode must be set (flag –105 clear).
Numeric mode must not be set (flag –3 clear).
Example: Find the gradient of the following function of the spatial variables x, y, and z:
2x
2
y 3y
2
z zx+ +
Command: DERIV(2*X^2*Y+3*Y^2*Z+Z*X, [X,Y,Z])
EXPAND(ANS(1))
Result: [4*Y*X+Z,2*X^2+6*Z*Y,X+3*Y^2]
See also: DERVX, dn, ∂, POTENTIAL
DERVX
Type: Function
Description: Returns the derivative of a function with respect to the current variable. This variable must not
exist as a variable stored in the current directory path.
Access: Calculus, !Ö or P CALCULUS or !Ö DERIV . & INTEG .
Input: The function or list of functions to be differentiated.
Output: The derivative, or a vector of the derivatives, of the function or functions.
Flags: Exact mode must be set (flag –105 clear).
Numeric mode must not be set (flag –3 clear).
See also: DERIV, dn, ∂
DESOLVE
Type: Command
Description: Solves certain first-order ordinary differential equations with respect to the current variable.
Access: Symbolic solve, !Î or calculus, !Ö DIFFERENTIAL EQNS .
Input: Level 2/Argument 1: A first-order differential equation.
Level 1/Argument 2: The function to solve for.
Output: The solution to the equation, either y as a function of x or x as a function of y, or x and y as
functions of a parameter.
Flags: Exact mode must be set (flag –105 clear).
Numeric mode must not be set (flag –3 clear).
Example: Solve the following differential equation:
y′ x( ) 2 y x( )+ e
3
x
=
Command: DESOLVE(d1Y(X)+2*Y(X)=EXP(3*X),Y(X))