# Lim from pos for an integral

1. Dec 15, 2008

### tomboi03

Prove: If f is integrable on [a,b] then
lim $$\int$$(a,x) f=0

I put If F is integrable for every E>0, partition,P, U(f,P) - L(f,P) <E
This also means that f is integrable on [a,a+]

If $$\int$$ (x,x) f(x) dx =0
F(x)-F(x)=0
Since f is integrable, if can be differentiable (he said that this was wrong)
lim $$\int$$ (a,x) f(x) dx
x$$\rightarrow$$a+

lim $$\int$$ (a,x) f(x) dx
x$$\rightarrow$$a

lim $$\int$$ (a,x) f(x) dx
x$$\rightarrow$$a-

are all equal then
lim $$\int$$ (a,x) f(x) dx
x$$\rightarrow$$a+

what am i doing wrong?

2. Dec 15, 2008

### mutton

"[a, a+]" is not an interval.

The limits of integration should not depend on x.

Integrability does not imply differentiability. For example, |x| is integral on [-1, 1] but not differentiable at 0.

It's not clear how the parts of your proof are connected.