# Finding a Riemann sum

• Apr 18th 2009, 01:12 PM
student_forever
Finding a Riemann sum
Please, help me to solve this problem!!!!(Crying)

Wite a left Riemann sum, with n=5, that approximates the values of ln x dx over interval [1,11]

I found x=b-a/n=111/5=2 what's the next step?

thank you!!!
• Apr 18th 2009, 03:53 PM
stapel
If n = 5, then how many sub-intervals will there be? If the total with is 10 units, what will be the width of those sub-intervals?

If the first left-hand endpoint is x = 1, then what is the second left-hand endpoint? What is the third? Etc.

What is the value of ln(x) for each of these endpoint values?

Multiplying each value of ln(x) by the width of the interval, what "area" values do you get?

What then is the sum of the areas?

(Wink)
• Apr 19th 2009, 11:43 AM
student_forever
Can you write down the solution, please?
The words make me more confused :(
• Apr 19th 2009, 12:58 PM
student_forever
I got it, finally (Clapping)
(ln(1)+ln(3)+ln(5)+ln(7)+ln(9))*2=13.702