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Ch. 5 - Integration
5์žฅ, ๋ฌธ์ œ 5.R.9d

Integration by Riemann sums Consider the integral โˆซโ‚โด (3๐“โ€• 2) d๐“.


(a) Evaluate the right Riemann sum for the integral with n = 3 .

๊ฒ€์ฆ๋œ ๋‹จ๊ณ„๋ณ„ ์•ˆ๋‚ด
1
Step 1: Understand the problem. The integral โˆซโ‚โด (3๐“ - 2) d๐“ represents the area under the curve of the function f(๐“) = 3๐“ - 2 from ๐“ = 1 to ๐“ = 4. To approximate this integral using the right Riemann sum, we divide the interval [1, 4] into n = 3 subintervals.
Step 2: Determine the width of each subinterval. The width ฮ”๐“ is calculated as ฮ”๐“ = (b - a) / n, where a = 1, b = 4, and n = 3. Substitute these values into the formula to find ฮ”๐“.
Step 3: Identify the right endpoints of each subinterval. The right endpoints are calculated as ๐“โ‚ = a + ฮ”๐“, ๐“โ‚‚ = a + 2ฮ”๐“, and ๐“โ‚ƒ = a + 3ฮ”๐“. Use the value of ฮ”๐“ from Step 2 to compute these endpoints.
Step 4: Evaluate the function f(๐“) = 3๐“ - 2 at each right endpoint. Substitute the values of ๐“โ‚, ๐“โ‚‚, and ๐“โ‚ƒ into the function to find f(๐“โ‚), f(๐“โ‚‚), and f(๐“โ‚ƒ).
Step 5: Compute the right Riemann sum. Multiply each function value f(๐“แตข) by the width ฮ”๐“ and sum them up: Right Riemann Sum = ฮ”๐“ ร— [f(๐“โ‚) + f(๐“โ‚‚) + f(๐“โ‚ƒ)]. This gives the approximation for the integral.

๋น„์Šทํ•œ ๋ฌธ์ œ์— ๋Œ€ํ•œ ๊ฒ€์ฆ๋œ ์˜์ƒ ๋‹ต๋ณ€:

์ด ์˜์ƒ ํ•ด๋ฒ•์€ ์œ„ ๋ฌธ์ œ์— ๋„์›€์ด ๋œ๋‹ค๊ณ  ํŠœํ„ฐ๋“ค์ด ์ถ”์ฒœํ•œ ๊ฒƒ์ž…๋‹ˆ๋‹ค.
์˜์ƒ ๊ธธ์ด:
4m
๋„์›€์ด ๋˜์—ˆ๋‚˜์š”?

์ฃผ์š” ๊ฐœ๋…

์งˆ๋ฌธ์— ์˜ฌ๋ฐ”๋ฅด๊ฒŒ ๋‹ตํ•˜๊ธฐ ์œ„ํ•ด ๋ฐ˜๋“œ์‹œ ์ดํ•ดํ•ด์•ผ ํ•˜๋Š” ํ•ต์‹ฌ ๊ฐœ๋…๋“ค์€ ๋‹ค์Œ๊ณผ ๊ฐ™์Šต๋‹ˆ๋‹ค.

Riemann Sums

Riemann sums are a method for approximating the value of a definite integral by dividing the area under a curve into small rectangles. The sum of the areas of these rectangles provides an estimate of the integral's value. Depending on the chosen points (left, right, or midpoint) for the height of the rectangles, different types of Riemann sums can be calculated, which converge to the actual integral as the number of rectangles increases.
์ถ”์ฒœ ์˜์ƒ:

Definite Integral

A definite integral represents the signed area under a curve defined by a function over a specific interval [a, b]. It is denoted as โˆซโ‚แต‡ f(x) dx and can be interpreted as the limit of Riemann sums as the number of subdivisions approaches infinity. The Fundamental Theorem of Calculus connects differentiation and integration, allowing us to evaluate definite integrals using antiderivatives.
์ถ”์ฒœ ์˜์ƒ:
๊ฐ€์ด๋“œ ์ฝ”์Šค
05:43
Definition of the Definite Integral

Partitioning the Interval

Partitioning the interval involves dividing the range of integration into smaller subintervals, which is essential for calculating Riemann sums. For n subintervals, the width of each subinterval is ฮ”x = (b - a)/n. In this case, with n = 3 for the integral from 1 to 4, the interval is divided into three equal parts, allowing for the evaluation of the function at specific points to approximate the area under the curve.
์ถ”์ฒœ ์˜์ƒ:
08:44
Interval of Convergence
๊ด€๋ จ ์‹ค์ฒœ
๊ต๊ณผ์„œ ์งˆ๋ฌธ

Area of regions Compute the area of the region bounded by the graph of ฦ’ and the ๐“-axis on the given interval. You may find it useful to sketch the region.                                              

                                                                                                                                                                                    

 ฦ’(๐“) = 16โ€•๐“ยฒ on [โ€•4, 4]

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๊ต๊ณผ์„œ ์งˆ๋ฌธ

Find the average value of ฦ’(๐“) = eยฒหฃ on [0, ln 2] .

53
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๊ต๊ณผ์„œ ์งˆ๋ฌธ

Properties of integrals Suppose โˆซโ‚โด ฦ’(๐“) d๐“ = 6 , โˆซโ‚โด g(๐“) d๐“ = 4 and โˆซโ‚ƒโด ฦ’(๐“) d๐“ = 2 . Evaluate the following integrals or state that there is not enough information.


โ€•โˆซโ‚„ยน 2ฦ’(๐“) d๐“

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๊ต๊ณผ์„œ ์งˆ๋ฌธ

Evaluating integrals Evaluate the following integrals.                                                                                                                                         

                                                                                                                                                                   

 โˆซ (9๐“โธโ€•7๐“โถ) d๐“

55
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๊ต๊ณผ์„œ ์งˆ๋ฌธ

Area functions and the Fundamental Theorem Consider the function

ฦ’(t) = { t      if  โ€•2 โ‰ค t < 0

tยฒ/2    if    0 โ‰ค t โ‰ค 2

and its graph shown below. Let F(๐“) = โˆซโ‚‹โ‚หฃ ฦ’(t) dt and G(๐“) = โˆซโ‚‹โ‚‚หฃ ฦ’(t) dt.

(e) Evaluate F ''(โ€•1) and F ''(1). Interpret these values.

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๊ต๊ณผ์„œ ์งˆ๋ฌธ

Evaluating integrals Evaluate the following integrals.


โˆซโ‚€ยฒ (2๐“ + 1)ยณ d๐“

109
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