# delta and derivatives

#### AlexK

Joined May 23, 2007
34
Hello, I have a question

It is known that the derivative of a discontinuous function at the point of discontinuity is Delta*[F(x+)-F(x-)]
Now, in order to prove this we need to express the function as a sum of a continuous function ( K(x) ) and a number of steps, so we get:
F(x)'=K(x)' + Delta*[F(x+)-F(x-)]
But what should I do with K(x)' ? Can i say it is equal to zero? And if so, why?