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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 5.3.97a

Working with area functions Consider the function Ζ’ and the points a, b, and c.
(a) Find the area function A (𝓍) = βˆ«β‚Λ£ Ζ’(t) dt using the Fundamental Theorem.
Ζ’(𝓍) = cos 𝓍 ; a = 0 , b = Ο€/2 , c = Ο€

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Step 1: Recall the Fundamental Theorem of Calculus, which states that if A(𝓍) = βˆ«β‚Λ£ Ζ’(t) dt, then A'(𝓍) = Ζ’(𝓍). This means the derivative of the area function A(𝓍) is equal to the original function Ζ’(𝓍).
Step 2: To find the area function A(𝓍), integrate Ζ’(t) = cos(t) with respect to t from the lower limit a = 0 to the upper limit 𝓍. The integral of cos(t) is sin(t).
Step 3: Apply the definite integral formula: A(𝓍) = βˆ«β‚Λ£ Ζ’(t) dt = [sin(t)]ₐˣ. Substitute the limits of integration into the antiderivative.
Step 4: Substitute the lower limit a = 0 and the upper limit 𝓍 into the expression: A(𝓍) = sin(𝓍) - sin(0). Simplify the result using the fact that sin(0) = 0.
Step 5: The area function A(𝓍) is now expressed as A(𝓍) = sin(𝓍). This function represents the accumulated area under Ζ’(t) = cos(t) from t = 0 to t = 𝓍.

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Key Concepts

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

Fundamental Theorem of Calculus

The Fundamental Theorem of Calculus connects differentiation and integration, stating that if a function is continuous on an interval, then the integral of its derivative over that interval gives the net change of the function. Specifically, it allows us to evaluate definite integrals using antiderivatives, which is essential for finding area functions.
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Fundamental Theorem of Calculus Part 1

Definite Integral

A definite integral represents the signed area under a curve defined by a function over a specific interval [a, b]. It is calculated as the limit of Riemann sums and provides a numerical value that corresponds to the total accumulation of the function's values between the bounds, which is crucial for determining the area function A(x) in the given problem.
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Area Function

An area function A(x) is defined as the integral of a function f(t) from a constant lower limit a to a variable upper limit x. This function represents the accumulated area under the curve of f(t) from a to x, and it is essential for understanding how the area changes as x varies, particularly in the context of the problem involving the cosine function.
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Related Practice
Textbook Question

Zero net area Consider the function Ζ’(𝓍) = 𝓍² ― 4𝓍 .

(a) Graph Ζ’ on the interval 𝓍 β‰₯ 0.

Textbook Question

Mass from density A thin 10-cm rod is made of an alloy whose density varies along its length according to the function shown in the figure. Assume density is measured in units of g/cm. In Chapter 6, we show that the mass of the rod is the area under the density curve.

(a) Find the mass of the left half of the rod (0 ≀ x ≀ 5) .

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Textbook Question

Approximating areas Estimate the area of the region bounded by the graph of Ζ’(𝓍) = xΒ² + 2 and the x-axis on [0, 2] in the following ways.

(a) Divide [0, 2] into n = 4 subintervals and approximate the area of the region using a left Riemann sum. Illustrate the solution geometrically.

Textbook Question

The velocity in ft/s of an object moving along a line is given by v = Ζ’(t) on the interval 0 ≀ t ≀ 6 (see figure), where t is measured in seconds.


(a) Divide the interval [0,6] into n = 3 subintervals, [0,2] , [2,4] and [4,6]. On each subinterval, assume the object moves at a constant velocity equal to the value of v evaluated at the right endpoint of the subinterval, and use these approximations to estimate the displacement of the object on [0,6] (see part (a) of the figure)                                                                                                             

                                                                                                                                                                                                

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Textbook Question

Sigma notation Evaluate the following expressions.

(a)    10                                                                                                                                                                               

       βˆ‘ ΞΊ                                                                                                                                                                          

       ΞΊ=1                         

Textbook Question

Explain why or why not Determine whether the following statements are true and give an explanation or counterexample.

(a) Consider the linear function Ζ’(𝓍) = 2x + 5 and the region bounded by its graph and the x-axis on the interval [3,6]. Suppose the area of this region is approximated using midpoint Riemann sums. Then the approximations give the exact area of the region for any number of subintervals.

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