Where is this function differentiable?

In summary, differentiable refers to the smoothness of a function and its well-defined tangent line at every point. To determine if a function is differentiable at a specific point, we use the definition of a derivative. A function can be differentiable at some points but not others, usually due to sharp corners or discontinuities. Continuity refers to the absence of breaks or gaps in a function's graph, and a function can be continuous but not differentiable. However, a function cannot be differentiable but not continuous, as differentiability implies continuity but not vice versa.
  • #1
Omega017
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How do I go about determining where [tex] f(x,y) = \sqrt{|x| + |y|} [/tex] is differentiable?
 
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  • #2
A function is differentiable at a point if the function's partial derivatives exist and are continuous at that point. First, find the function's partial derivatives. The function is differentiable at all points where the partial derivatives are continuous.
For the points where the function's partial derivatives are not continuous, you will have to manually test the differentiability of the function using the definition of the derivative. However, for this particular function, a quick look at the cross-sections should let you know.
 
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Related to Where is this function differentiable?

1. What is meant by "differentiable" in the context of functions?

Differentiable refers to the property of a function where it is smooth and has a well-defined tangent line at every point. In other words, a differentiable function does not have any sharp corners or breaks in its graph.

2. How do you determine if a function is differentiable at a specific point?

To determine differentiability at a point, we can use the definition of a derivative. If the limit of the difference quotient (change in y divided by change in x) exists as x approaches the given point, then the function is differentiable at that point.

3. Can a function be differentiable at some points but not others?

Yes, it is possible for a function to be differentiable at some points but not others. This occurs when the function has a sharp corner, vertical tangent, or discontinuity at certain points.

4. What is the difference between differentiability and continuity?

Continuity refers to the property of a function where there are no breaks or gaps in its graph. A function can be continuous but not differentiable, as it may have a sharp corner or cusp at a certain point. Differentiability requires the function to be smooth and have a well-defined tangent line at every point.

5. Can a function be differentiable but not continuous?

No, a function cannot be differentiable but not continuous. If a function is differentiable at a point, it must also be continuous at that point. This is because differentiability implies continuity, but the reverse is not necessarily true.

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