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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 5.3.13a

Area functions The graph of ƒ is shown in the figure. Let A(x) = ∫₋₂ˣ ƒ(t) dt and F(x) = ∫₄ˣ ƒ(t) dt be two area functions for ƒ. Evaluate the following area functions.
(a) A (―2)
Graph of a function with labeled areas: 8, 9, and 17, illustrating integral calculations over specified intervals.

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Understand the problem: We are tasked with evaluating A(-2), where A(x) = ∫₋₂ˣ ƒ(t) dt. This means we need to calculate the definite integral of the function ƒ(t) from -2 to -2.
Recall the property of definite integrals: If the upper and lower limits of the integral are the same, the integral evaluates to 0. Mathematically, ∫ₐₐ ƒ(t) dt = 0.
Apply this property to A(-2): Since the limits of integration are both -2, the integral evaluates to 0.
Conclude that A(-2) = 0 based on the property of definite integrals.
No further calculations are needed as the result is determined by the fundamental property of definite integrals.

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Key Concepts

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

Definite Integral

A definite integral represents the signed area under a curve between two points on the x-axis. It is calculated using the integral symbol and limits of integration, providing a numerical value that corresponds to the total area, accounting for areas above and below the x-axis. In this context, A(x) and F(x) are defined as definite integrals of the function ƒ(t) over specified intervals.
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Definition of the Definite Integral

Area Function

An area function, such as A(x) or F(x), is a function that gives the accumulated area under a curve from a specific starting point to a variable endpoint x. It is defined as the integral of a function from a constant lower limit to x, allowing for the evaluation of how the area changes as x varies. This concept is crucial for understanding how to compute areas based on the graph provided.
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Fundamental Theorem of Calculus

The Fundamental Theorem of Calculus links the concept of differentiation and integration, stating that if F is an antiderivative of f on an interval, then the integral of f from a to b is equal to F(b) - F(a). This theorem is essential for evaluating area functions, as it allows us to compute the definite integral by finding the antiderivative of the function and applying the limits of integration.
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Related Practice
Textbook Question

Using properties of integrals Use the value of the first integral I to evaluate the two given integrals. 

I = ∫₀¹ (𝓍³ ― 2𝓍) d𝓍 = ―3/4

(a) ∫₀¹ (4𝓍―2𝓍³) d𝓍

Textbook Question

Area functions for linear functions Consider the following functions ƒ and real numbers a (see figure).

(a) Find and graph the area function A (𝓍) = ∫ₐˣ ƒ(t) dt .

ƒ(t) = 2t + 5 , a = 0

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Textbook Question

Use Table 5.6 to evaluate the following indefinite integrals.                                                                                                               

                                                                                                                                                                  

 (a) ∫ e¹⁰ˣ d𝓍

Textbook Question

{Use of Tech} Midpoint Riemann sums with a calculator Consider the following definite integrals.

(a) Write the midpoint Riemann sum in sigma notation for an arbitrary value of n.


∫₁⁴ 2√𝓍 d𝓍

Textbook Question

Sigma notation Express the following sums using sigma notation. (Answers are not unique.)

(a) 1 + 2 + 3 + 4 + 5

Textbook Question

Using properties of integrals Use the value of the first integral I to evaluate the two given integrals. 

I = ∫₀^π/2 (cos θ ― 2 sin θ) dθ = ―1

(a) ∫₀^π/2 (2 sin θ ― cos θ) dθ