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Advanced Engineering Mathematics
10th Edition
ISBN: 9780470458365
Author: Erwin Kreyszig
Publisher: Wiley, John & Sons, Incorporated
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Question

Transcribed Image Text:1. Consider the function f defined by
f(x, y) =
x²y + y²x
x² + y²
0
if (x, y) (0,0);
"
if (x, y)=(0,0).
(a) Show that f is continuous at (0,0). (Hint: Evaluate the appro-
priate limit by changing to polar coordinates.)
(b) Using the principal definition of partial derivatives, show that
(0,0) exists and equals 0.
af
მე
(c) You may assume that
af
მყ
(0, 0) exists and is equal to 0. Using the
definition of differentiablity of a multivariable function, explain
why f is not differentiable at (0,0). (Hint: Investigate the exis-
tence or otherwise of the appropriate limit by changing to polar
coordinates.)
2. Consider the region R in the xy-plane given by
R={(x,y) R² x ≥ 0, y ≥ 0 and 1 ≤ x² + y² ≤ 2}.
(a) Sketch the region R.
(b) By changing to polar coordinates evaluate the double integral
y sin (π (x² + y²))
√x² + y²
dx dy.
Recall that Cartesian and polar coordinates are related by
(x, y) = (r cos 0, r sin 0),
✓
(1)
where r = √√√x² + y², and 0 ≤ 0 < 27. You may assume that the
Jacobian for the change of variables (1) is given by
(x, y)
ǝ (r, 0)
= 1.
Expert Solution
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