Continuity of partial derivatives

In summary, continuity of partial derivatives refers to the concept that a function has continuous partial derivatives at a given point if the derivatives exist and are equal to the value of the function at that point. If a function has continuous partial derivatives at a point, it is also differentiable at that point. However, the reverse is not always true. We can test for continuity of partial derivatives by using the definition of continuity or the existence of the partial derivatives. A function cannot have continuous partial derivatives but not be continuous. Continuity of partial derivatives is important in mathematics because it allows us to analyze multivariable functions and apply important concepts such as the chain rule and Taylor's theorem.
  • #1
Shaybay92
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What exactly does it mean for a function to have continuous partial derivatives? How do we see this?
 
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  • #2
Well, first of all the partial derivative(s) must exist. This is a function

[tex]x\mapsto D_if(x)[/tex]

(where D_if denote the i-th partial derivative), and this function itself may be continuous.

If all its partial derivatives exist and are continuous, then the function is differentiable, in the sense that its total derivative exists.
 

FAQ: Continuity of partial derivatives

What does continuity of partial derivatives mean?

Continuity of partial derivatives refers to the concept that a function has continuous partial derivatives at a given point if the derivatives exist and are equal to the value of the function at that point.

How is continuity of partial derivatives related to differentiability?

If a function has continuous partial derivatives at a point, it is also differentiable at that point. However, the reverse is not always true - a function can be differentiable but not have continuous partial derivatives at a point.

How can we test for continuity of partial derivatives?

We can use the definition of continuity to test for the continuity of partial derivatives. This means checking if the limit of the partial derivatives exists and is equal to the value of the function at the given point. We can also use the existence of the partial derivatives to determine continuity.

Can a function have continuous partial derivatives but not be continuous?

No, if a function has continuous partial derivatives at a point, it must also be continuous at that point. This is because the existence of partial derivatives implies that the function is continuous at that point.

Why is continuity of partial derivatives important in mathematics?

Continuity of partial derivatives is important because it allows us to analyze and understand the behavior of multivariable functions. It also helps us to determine if a function is differentiable at a given point and allows us to apply important mathematical concepts such as the chain rule and Taylor's theorem.

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