What is the derivative of max(u(x),v(x)) when u(x) and v(x) are given functions?

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In summary, the derivative of max(u(x),v(x)) depends on the cases when u(x)>v(x) and when v(x)>u(x). However, even if u(x) and v(x) are not continuous, max(u(x),v(x)) can still be differentiable. On the other hand, there are cases where max(u(x),v(x)) is not differentiable, such as when u(x) and v(x) have opposite signs.
  • #1
Dansuer
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What is the derivative of the function f(x)= max(u(x),v(x)) ?
where u(x) and v(x) are two given function
 
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  • #2
Try looking at the two cases when u(x)>v(x) and when v(x)>u(x)
 
  • #3
Office_Shredder said:
Try looking at the two cases when u(x)>v(x) and when v(x)>u(x)

That is a good place to start, but max(u(x),v(x)) can be differentiable when u(x) and v(x) are not even continuous.

For example
u(x) = 0 when x is rational, u(x) = 1 otherwise
v(x) = 1 when x is rational , v(x) = 0 otherwise
 
  • #4
AlephZero said:
That is a good place to start, but max(u(x),v(x)) can be differentiable when u(x) and v(x) are not even continuous.

For example
u(x) = 0 when x is rational, u(x) = 1 otherwise
v(x) = 1 when x is rational , v(x) = 0 otherwise

Or max(u(x),v(x)) can not be differentiable, while u(x) and v(x) are:

For example:
u(x)=x and v(x)=-x

Then max(u(x),v(x))=|x| which is not differentiable in 0.
 

FAQ: What is the derivative of max(u(x),v(x)) when u(x) and v(x) are given functions?

What is the derivative of max(u(x),v(x))?

The derivative of max(u(x),v(x)) is determined by comparing the derivatives of u(x) and v(x) at a given point. If the derivative of u(x) is greater than the derivative of v(x), then the derivative of max(u(x),v(x)) is equal to the derivative of u(x). Otherwise, if the derivative of v(x) is greater, then the derivative of max(u(x),v(x)) is equal to the derivative of v(x).

How do you find the derivative of max(u(x),v(x))?

To find the derivative of max(u(x),v(x)), you need to compare the derivatives of u(x) and v(x) at a given point. If the derivative of u(x) is greater than the derivative of v(x), then the derivative of max(u(x),v(x)) is equal to the derivative of u(x). Otherwise, if the derivative of v(x) is greater, then the derivative of max(u(x),v(x)) is equal to the derivative of v(x).

Can the derivative of max(u(x),v(x)) be negative?

Yes, the derivative of max(u(x),v(x)) can be negative. This happens when the derivative of v(x) is greater than the derivative of u(x) at a given point, resulting in the derivative of max(u(x),v(x)) being equal to the derivative of v(x).

What is the importance of calculating the derivative of max(u(x),v(x))?

Calculating the derivative of max(u(x),v(x)) is important in optimization problems, where we want to find the maximum of a function that depends on multiple variables. By finding the derivative, we can determine the slope of the function at a given point and use that information to find the maximum value.

Can the derivative of max(u(x),v(x)) be undefined?

No, the derivative of max(u(x),v(x)) cannot be undefined. This is because the derivative is defined as the limit of the difference quotient, and since we are comparing the derivatives of u(x) and v(x), at least one of them will have a defined derivative at a given point.

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