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Homework Help: Trapezoidal Rule

  1. May 8, 2012 #1
    1. The problem statement, all variables and given/known data
    Part b.

    2. Relevant equations

    3. The attempt at a solution
    Well I thought the trapezoidal rule was:
    [tex]\int_a^b f(x)dx = \frac{b-a}{2n}[f(1)+2f(2)+2f(3)+...+f(n)][/tex]

    But when I did that I got the wrong answer and the work shows a completely different formula that I didn't know:

    The part I'm confused about is the (2((66+60)/2)+....)
  2. jcsd
  3. May 8, 2012 #2


    Staff: Mentor

    (66+60)/2 is the avg height and 2 is thw dith of the segment so then 2*(66+60)/2 = area of that segment. add them up to get the approx area under the curve.
  4. May 8, 2012 #3
    Why is there an 2, then 3, then 4, then1 infront of each of the areas of the segments :|
  5. May 8, 2012 #4


    Staff: Mentor

    The first subinterval is of width 2 (sec); the 2nd's width is 3 sec; the 3rd's width is 4 sec; the last subinterval's width is 1.
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