# Proof that f(x)=F'(x)…that derivative of antiderivative equals original function

Is there any proof for this as far i can find fundamental theorem is used to proof this...And fundamental theorem is proven using this.

So to me it sounds like chicken egg thing...

I have been doing this whole day...

http://en.wikipedia.org/wiki/Fundamental_theorem_of_calculus#cite_note-5

in link above it says that since f(x)= A'(x) therefore A(x)=F(x);

and when i go to understand why F'(x) = f(x)...or in this Case How antiderivative of integral A equals A. I get referenced back to fundamental theorem. Is it using itself as a proof?

• does this help? math.stackexchange.com/questions/663487/… – TooTone Mar 16 '14 at 23:36
• forexample: at line where it says According to the mean value theorem for integration, there exists a real number it makes integral equal to area derived from mean value theorem. But Why. For to proof that integral equals area it needs to be proven that derivative of integral equals original function. Because what can be proven is that original function f(x) = A'(x). – Muhammad Umer Mar 17 '14 at 0:55
This is true by definition. We say a function $F(x)$ is an antiderivative of $f(x)$ when $F'(x) = f(x)$.
• @MuhammadUmer You are getting confused by the notation. Sometimes, $F(x)$ is used to mean an antiderivative of $f(x)$. Other times, $F(x)$ is defined as $\int_a^x f(t) dt$. You will have to read the text to determine which one of these is meant in a particular case. – augurar Mar 17 '14 at 1:14