# Riemann Sum

• Apr 3rd 2008, 03:49 PM
A5HLEY
Riemann Sum
Find L4 for f(x)=49cos(pi/2) from [2pi/4,2pi/2]

I thought it would just be zero since there aren't any x's in f(x)? Apparently that's incorrect though. Any help would be wonderful! :)
• Apr 3rd 2008, 04:17 PM
TheEmptySet
Quote:

Originally Posted by A5HLEY
Find L4 for f(x)=49cos(pi/2) from [2pi/4,2pi/2]

I thought it would just be zero since there aren't any x's in f(x)? Apparently that's incorrect though. Any help would be wonderful! :)

Either you have a typo or you book has one becuase

$f(x)=49\cos(\pi/2)=0$ for all values of x.

so the left endpoint sum would be

$L_4=\sum_{i=0}^{3}f(\frac{\pi}{2}+i\frac{\pi}{8})\ frac{\pi}{8}=0$

since f(x)=0 for all values of x.