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Example 5

Find a set on which h(x,y) = xy + cos11_partial_differentiation-106.gifis continuous.

  • xy is continuous for x > 0.
  • x2 is continuous for all x.
  • x2 - y is continuous for all (x, y).
  • 11_partial_differentiation-107.gif is continuous for x2 - y > 0.
  • cos11_partial_differentiation-108.gif is continuous for x2 - y > 0.
  • xy + cos11_partial_differentiation-109.gif is continuous for x > 0 and x2 - y > 0.

11_partial_differentiation-111.gif

Figure 11.2.4

Answer h(x, y) is continuous on the set of all (x, y) such that x > 0 and x2 - y > 0. The set is shown in Figure 11.2.4.


Last Update: 2006-11-15