# riemann sum

• Nov 14th 2006, 11:04 PM
gracy
riemann sum
If f(x)>= 0 then what is geometrical intrepretation of Riemann sum
• Nov 14th 2006, 11:06 PM
gracy
plz need help
If f(x) takes both positive and negative values,what is geometric intrepretation of Riemann sum?
• Nov 14th 2006, 11:14 PM
gracy
plz help
explain integrability theorem
• Nov 15th 2006, 04:48 AM
ThePerfectHacker
Quote:

Originally Posted by gracy
If f(x)>= 0 then what is geometrical intrepretation of Riemann sum

If $f(x)\geq 0$ and the sum exists (sufficiently a countinous function) then it represents the area below the curve and the x-axis. And if the function gets negative you can think of it as "negative" area.

Quote:

explain integrability theorem
1)If a function is countinous on some closed interval then the integral (Riemann) exists.

2)The Riemann integral is well-defined by partitioning if it exists. That is no matter how you partition your interval for the Riemann sum it is the same.

3*)I think the necessary and sufficient condition on 1) is that the function be defined on a closed interval and be discountinous at countably many points. But that definition is often not presented in a Calculus course for it is too advanced. If you can understand it use it.