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Unformatted text preview: Math 23 Sections 110113 B. Dodson Week 5 Homework: 14.1 graphs, level curves/surfaces, contour maps 14.2 limits Problem 14.1.9b: Find the domain of f ( x, y, z ) = e √ z x 2 y 2 . Solution: By definition, the domain of a function defined by a formula is the collection of points for which the formula makes sense (rather than by specifiying a particular subset). We analyze the formula in pieces (as a composite of functions). For the exponential function, e w is defined for all w , so this gives no restriction. Next, the squareroot is only defined on nonnegative input, so we must restrict ( x, y, z ) so that z x 2 y 2 is nonnegative. We check the boundary points, ones for which 0 = z x 2 y 2 , or z = x 2 + y 2 ; which we recognize as an elliptic paraboloid. This boundary surface divides 3space into two regions, and we see z x 2 y 2 positive on the region above the paraboloid, so domain( f ) = { ( x, y, z ) so z ≥ x 2 + y 2 } . 2 ....
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 Spring '06
 YUKICH
 Limits

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