1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Definite integral using Riemann sums?

  1. Nov 11, 2011 #1
    I'm reviewing my Calc 1 material for better understanding. So, I was reading about the area under a curve and approximating it using Riemann sums. Now, I understand the method, but I was a little confused by finding xi*. I know there is a formula for it xi*=a+Δx(i). What does the "i" stand for?

    I was looking at a problem for f(x)=cos(x) and its bounded by x=0 and x=∏/2, with four subintervals. Also, the problem states to use the xi sample points as the midpoints. I understand how to do it, but I don't get what the "i" represents.

    If this helps x1*=∏/16, x2*=3∏/16, x3*=5∏/16, and x4*=7∏/16

    Thanks
     
  2. jcsd
  3. Nov 11, 2011 #2

    lurflurf

    User Avatar
    Homework Helper

    i is just the number of the interval
    x1*=∏/16, x2*=3∏/16, x3*=5∏/16, and x4*=7∏/16
    could be written
    xi*=(∏/16)(2i-1)
    for i=1,2,3,4
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook