Chapter 4: Partial Differentiation
Section 4.2: Higher-Order Partial Derivatives
If f=sinx y and a,b=π/6,π/3, obtain all second partial derivatives, both at x,y and at a,b.
Table 4.2.3(a) lists the simplified forms of the second partial derivatives of f, both at x,y and at a,b.
Table 4.2.3(a) Second partials of f at x,y and π/6,π/3
Maple Solution - Interactive
Define f as an expression and use the second-partial operators from the Calculus palette.
Context Panel: Assign Name
Second partial derivatives at x,y
Calculus palette: Second-partials operators
Context Panel: Evaluate and Display Inline
∂2∂x2 f = −y2⁢sin⁡x⁢y
∂2∂ y⁢∂ x f = cos⁡x⁢y−x⁢y⁢sin⁡x⁢y
∂2∂ x⁢∂ y f = cos⁡x⁢y−x⁢y⁢sin⁡x⁢y
∂2∂y2 f = −x2⁢sin⁡x⁢y
Second partial derivatives at a,b
Expression palette: Evaluation template
∂2∂x2 fx=a|f(x)x=π/6,y=π/3 = −19⁢π2⁢sin⁡118⁢π2
∂2∂ y⁢∂ x fx=a|f(x)x=π/6,y=π/3 = cos⁡118⁢π2−118⁢π2⁢sin⁡118⁢π2
∂2∂y2 fx=a|f(x)x=π/6,y=π/3 = −136⁢π2⁢sin⁡118⁢π2
∂2∂ x⁢∂ y fx=a|f(x)x=π/6,y=π/3 = cos⁡118⁢π2−118⁢π2⁢sin⁡118⁢π2
Alternatively, define the second partial derivatives as functions. Every subscripted name must be an Atomic Identifier.
Calculus palette: Second-partial operators
Context Panel: Assign Function
f__xxx,y=∂2∂x2 f→assign as functionf__xx
f__xyx,y=∂2∂ y⁢∂ x f→assign as functionf__xy
f__yyx,y=∂2∂y2 f→assign as functionf__yy
f__yxx,y=∂2∂ x⁢∂ y f→assign as functionf__yx
Obtain the second partial derivatives at x,y
Obtain the second partial derivatives at a,b
f__xxx,y = −y2⁢sin⁡x⁢y
f__xxπ6,π3 = −19⁢π2⁢sin⁡118⁢π2
f__xyx,y = cos⁡x⁢y−y⁢x⁢sin⁡x⁢y
f__xyπ6,π3 = cos⁡118⁢π2−118⁢π2⁢sin⁡118⁢π2
f__yxx,y = cos⁡x⁢y−y⁢x⁢sin⁡x⁢y
f__yxπ6,π3 = cos⁡118⁢π2−118⁢π2⁢sin⁡118⁢π2
f__yyx,y = −x2⁢sin⁡x⁢y
f__yyπ6,π3 = −136⁢π2⁢sin⁡118⁢π2
Maple Solution - Coded
If f is an expression, the simplified forms for its four second partial derivatives are obtained with the diff command. Evaluation at a,b is obtained with the eval command. The names to which the derivatives have been assigned are all Atomic Identifiers.
Assign the expression to the name f.
Second partials at x,y
Second partials at a,b
If f is a function, its four second partial derivatives are obtained with the D-operator. Evaluation at a,b is immediate since the D-operator returns derivatives as functions.
Define the function f.
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