- #1
NasuSama
- 326
- 3
Homework Statement
Given that:
[itex]
f(x,y) =
\begin{cases}
xy/(x² + y²), & \text{if }(x,y) \neq (0,0) \\
3n+1, & \text{if }(x,y) = (0,0)
\end{cases}
[/itex]
Discuss the continuity of that function from E² to ℝ.
Homework Equations
- Definition of continuity
- Definition of uniform continuity
The Attempt at a Solution
First, I said that f(x,y) is continuous everywhere except at (0,0) since ½ and 0 occur when (x,y) = (0,0) [can't put them in formal proof].
I want to test if f(x,y) is uniformly continuous. Using the definition of uniform continuity, [itex]\forall \epsilon > 0 \exists \delta > 0[/itex] such that:
If [itex]|(x,y) - (a,b)| < \delta[/itex] then [itex]|f(x,y) - f(a,b)| < \epsilon[/itex]
Given these intervals, I have:
[itex]|(x,y) - (a,b)| < \delta[/itex]
[itex]√((x - a)² + (y - b)²) < \delta[/itex] ← I'm not quite sure if this is correct.
[itex]|f(x,y) - f(a,b)| < \epsilon[/itex]
[itex]|xy/(x² + y²) - ab/(a² + b²)| < \epsilon[/itex] ← I'm stuck here. I don't know how to get from delta interval to here and figure out the appropriate substitution of [itex]\delta[/itex] and [itex]\epsilon[/itex]