# Identify distribution by a constant function [duplicate]

Possible Duplicate:
On distributions over $\mathbb R$ whose derivatives vanishes

Why can I identify a distribution $G \in \mathcal{D}'((a,b))$, $\partial G = 0$ by a constant function?

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## marked as duplicate by t.b., Davide Giraudo, Dylan Moreland, Pedro Tamaroff, Jonas TeuwenMay 21 '12 at 23:36

Hint: fix a test function $\psi_0$ of integral $1$ and for $\phi\in \mathcal D((a,b))$, put $$f(x):=\int_a^x\varphi(t)dt-\int_a^b\varphi(t)dt\int_a^x\psi_0(t)dt.$$ Check that $f$ is a test function, and compute $f'$. Then compute $G(f')$ to get the wanted result.