See also: CLEAR, DROPN

DERIV

Type:

Function

Description:

Returns the partial derivatives of a function, with respect to the specified variables.

Access:

Calculus, PCALCULUS or !ÖDERIV. & 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:

 

2x2y + 3y2z + 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 PCALCULUS or !ÖDERIV. & 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, !Îor calculus, !ÖDIFFERENTIAL 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) + 2y(x) = e3x

Command:

DESOLVE(d1Y(X)+2*Y(X)=EXP(3*X),Y(X))

3-56 Full Command and Function Reference