The expression for the change of the variable z is Δz = (0.9 · x² + 0.6 · y²) · cos (x³ + y³).
How to find the total differential of a multivariate function
In this question we must apply the concept of total differential to determine the change of the variable z in terms of the changes in variables x and y. That is:
[tex]\Delta z = \frac{\partial f}{\partial x}\cdot \Delta x + \frac{\partial f}{\partial y}\cdot \Delta y[/tex] (1)
If we know that z = sin (x³ + y³), Δx = 0.3 and Δy = 0.2, then the expression for the change of z is:
[tex]\Delta z = 3\cdot \cos (x^{3}+y^{3})\cdot x^{2}\cdot (0.3)+3\cdot \cos (x^{3}+y^{3})\cdot y^{2}\cdot (0.2)[/tex]
Δz = (0.9 · x² + 0.6 · y²) · cos (x³ + y³)
The expression for the change of the variable z is Δz = (0.9 · x² + 0.6 · y²) · cos (x³ + y³).
To learn more on rate of changes: https://brainly.com/question/12786410
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