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## Is the sum of differentiable functions differentiable?

The sum (or difference) of two differentiable functions is differentiable and is the sum (or difference) of their derivatives. The product of two differentiable functions, f and g, is itself differentiable.

**Can the sum of two non differentiable functions be differentiable?**

What is true, however, is the fact that sum of a differentiable function and a nondifferentiable function is nondifferentiable. This is true because differentiable functions are closed under subtraction, i.e. they comprise a subgroup of all functions.

### How do you prove a function is differentiable in real analysis?

First, we will start with the definition of derivative. If that limit exits, the function is called differentiable at c. If f is differentiable at every point in D then f is called differentiable in D. Other notations for the derivative of f are or f(x).

**How do you prove that every differentiable function is continuous?**

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- Differentiable Implies Continuous. Theorem: If f is differentiable at x0, then f is continuous at x0.
- number – this won’t change its value. lim f(x) – f(x0) = lim.
- = f�(x) 0· = 0. (Notice that we used our assumption that f was differentiable when we wrote down f�(x).)

## How do you know if a function is differentiable or not?

A function is formally considered differentiable if its derivative exists at each point in its domain, but what does this mean? It means that a function is differentiable everywhere its derivative is defined. So, as long as you can evaluate the derivative at every point on the curve, the function is differentiable.

**When a function is non differentiable?**

A function is non-differentiable when there is a cusp or a corner point in its graph. For example consider the function f(x)=|x| , it has a cusp at x=0 hence it is not differentiable at x=0 .

### Can a non differentiable function have a derivative?

In the case of functions of one variable it is a function that does not have a finite derivative. For example, the function f(x)=|x| is not differentiable at x=0, though it is differentiable at that point from the left and from the right (i.e. it has finite left and right derivatives at that point).

**How do you find a function is differentiable or not?**

## Does continuously differentiable imply continuous?

There are connections between continuity and differentiability. Differentiability Implies Continuity If is a differentiable function at , then is continuous at . If is not continuous at , then is not differentiable at . Thus from the theorem above, we see that all differentiable functions on are continuous on .

**Which function is not differentiable?**