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Ch. 5 - Integration
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Not the one you use?Change textbook
Chapter 5, Problem 5.1.63

{Use of Tech} Sigma notation for Riemann sums Use sigma notation to write the following Riemann sums. Then evaluate each Riemann sum using Theorem 5.1 or a calculator.
The midpoint Riemann sum for f(x) = x³ on [3,11] with n = 32.

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Step 1: Understand the problem. We are tasked with writing the midpoint Riemann sum for the function f(x) = x³ on the interval [3, 11] with n = 32 using sigma notation. Then, we need to evaluate the sum using Theorem 5.1 or a calculator.
Step 2: Divide the interval [3, 11] into n = 32 subintervals. The width of each subinterval, Δx, is calculated as Δx = (b - a) / n, where a = 3, b = 11, and n = 32. Use MathML: (11-3)32.
Step 3: Determine the midpoint of each subinterval. The midpoint of the i-th subinterval is given by x_i = a + (i - 0.5)Δx, where i ranges from 1 to n. Use MathML: xi=a+(i-0.5)Δx.
Step 4: Write the Riemann sum in sigma notation. The midpoint Riemann sum is expressed as S = Σ f(x_i)Δx, where i ranges from 1 to n. Substitute f(x) = x³ and Δx from Step 2 into the formula. Use MathML: i1x3Δx.
Step 5: Evaluate the Riemann sum using Theorem 5.1 or a calculator. Plug in the values for Δx and x_i into the sigma notation and compute the sum. This step involves numerical computation, which can be done using a calculator or software.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Riemann Sums

Riemann sums are a method for approximating the definite integral of a function over an interval. They involve partitioning the interval into smaller subintervals, calculating the function's value at specific points within these subintervals, and summing the products of these values and the widths of the subintervals. The midpoint Riemann sum specifically uses the midpoint of each subinterval to evaluate the function, providing a more accurate approximation than using left or right endpoints.
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Introduction to Riemann Sums

Sigma Notation

Sigma notation is a concise way to represent the sum of a sequence of terms. It uses the Greek letter sigma (Σ) to indicate summation, along with an index of summation that specifies the starting and ending values. For Riemann sums, sigma notation allows us to express the sum of function values multiplied by the width of the subintervals in a compact form, making it easier to manipulate and evaluate mathematically.
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Theorem 5.1 (Fundamental Theorem of Calculus)

Theorem 5.1, often referred to as the Fundamental Theorem of Calculus, establishes a connection between differentiation and integration. It states that if a function is continuous on a closed interval, then the definite integral of the function can be computed using its antiderivative. This theorem allows us to evaluate Riemann sums by finding the antiderivative of the function and applying the limits of integration, thus simplifying the process of calculating the area under the curve.
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Fundamental Theorem of Calculus Part 1
Related Practice
Textbook Question

Limits of sums Use the definition of the definite integral to evaluate the following definite integrals. Use right Riemann sums and Theorem 5.1.


∫₃⁷ (4𝓍 + 6) d𝓍

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Textbook Question

Identifying Riemann sums Fill in the blanks with an interval and a value of n.


4

∑ ƒ (1.5 + k) • 1 is a midpoint Riemann sum for f on the interval [ ___ , ___ ]

k = 1

with n = ________ .

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Textbook Question

Identifying definite integrals as limits of sums Consider the following limits of Riemann sums for a function ƒ on [a,b]. Identify ƒ and express the limit as a definite integral.                                

          n                                                                                                                                                                              

    lim   ∑   𝓍*ₖ (ln 𝓍*ₖ) ∆𝓍ₖ on [1,2]                                                                                                                                                                            

  ∆ → 0   k=1                                                                                                                                                                                                                      

77
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Textbook Question

Indefinite integrals Use a change of variables or Table 5.6 to evaluate the following indefinite integrals. Check your work by differentiating.                                                                                  

                                                                                                                                                                    

 ∫ d𝓍 / (√1 ― 9𝓍²)

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Textbook Question

Symmetry in integrals Use symmetry to evaluate the following integrals.

∫₋π/₂^π/² 5 sin θ dθ

245
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Textbook Question

Multiple substitutions If necessary, use two or more substitutions to find the following integrals.                                                                                    

                                                                                                                                                                    

  ∫ d𝓍 / [√1 + √(1 + 𝓍)] (Hint: Begin with u = √(1 + 𝓍 .)  

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