a) it is not limitative to suppose that f(*) is differentiable in 0. In...

http://www.mathhelpforum.com/math-he...tml#post582679

... it has been extablished that if f(*) is differentiable in 0 is...

(1)

From (1) we derive...

(2)

... and...

(3)

... so that if for (3) is , if for (2) is and [finally...] if that means that is ...

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