Trapezoidal Rule Homework: Equations and Solutions

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In summary, the conversation is about the trapezoidal rule and the confusion surrounding the formula used to calculate the approximate area under the curve. The person initially thought the formula was \int_a^b f(x)dx = \frac{b-a}{2n}[f(1)+2f(2)+2f(3)+...+f(n)], but the work showed a different formula. They are confused about the presence of the numbers 2, 3, 4, and 1 in front of each area of the segments and the varying widths of the subintervals.
  • #1
iRaid
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Homework Statement


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Part b.


Homework Equations





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:
2dw9ekw.png


The part I'm confused about is the (2((66+60)/2)+...)
 
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  • #2
(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.
 
  • #3
Why is there an 2, then 3, then 4, then1 infront of each of the areas of the segments :|
 
  • #4
iRaid said:
Why is there an 2, then 3, then 4, then1 infront of each of the areas of the segments :|
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.
 

FAQ: Trapezoidal Rule Homework: Equations and Solutions

1. What is the Trapezoidal Rule?

The Trapezoidal Rule is a numerical method used to approximate the value of a definite integral. It involves dividing the area under a curve into trapezoids and summing their areas to estimate the total area.

2. How do I use the Trapezoidal Rule to approximate an integral?

To use the Trapezoidal Rule, you first need to determine the limits of integration and the function that you want to approximate the integral of. Then, divide the interval into smaller subintervals and calculate the area of each trapezoid using the formula A = (1/2)(b1 + b2)h, where b1 and b2 are the lengths of the two parallel sides and h is the height. Finally, sum the areas of all the trapezoids to get an approximation of the integral.

3. What is the error associated with the Trapezoidal Rule?

The error associated with the Trapezoidal Rule is dependent on the number of subintervals used in the approximation. The more subintervals, the smaller the error. The error can be calculated using the formula E = -(b-a)^3/12n^2*f''(c), where (b-a) is the interval, n is the number of subintervals, and f''(c) is the second derivative of the function at some point c within the interval.

4. Can the Trapezoidal Rule be used for any type of function?

Yes, the Trapezoidal Rule can be used for any continuous function. However, it is most accurate for functions that are smooth and have no sharp changes in direction.

5. How accurate is the Trapezoidal Rule compared to other numerical methods?

The accuracy of the Trapezoidal Rule depends on the number of subintervals used. With a large number of subintervals, it can be more accurate than other numerical methods such as the Midpoint Rule or Simpson's Rule. However, it is generally less accurate than more complex methods such as Gaussian Quadrature.

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