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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 5.2.63

Definite integrals from graphs The figure shows the areas of regions bounded by the graph of ฦ’ and the ๐“-axis. Evaluate the following integrals.




โˆซโ‚€แถœ |ฦ’(๐“)| d๐“

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1
Identify the interval from 0 to c on the x-axis and observe the graph of the function ฦ’(๐“) over this interval.
Since the integral is of the absolute value |ฦ’(๐“)|, note that all areas between the graph and the x-axis will be considered positive, regardless of whether ฦ’(๐“) is above or below the x-axis.
Break the interval [0, c] into subintervals where the function ฦ’(๐“) does not change sign (i.e., where it is either entirely positive or entirely negative).
For each subinterval, calculate the area between the graph of ฦ’(๐“) and the x-axis. If the function is negative on that subinterval, take the absolute value of the integral (which corresponds to the area).
Sum all these positive areas from each subinterval to find the value of the definite integral โˆซโ‚€แถœ |ฦ’(๐“)| d๐“.

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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 calculates the net area under a curve between two points on the x-axis. It sums the values of the function over the interval, considering areas above the x-axis as positive and below as negative. This concept is fundamental for interpreting integrals from graphs.
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Definition of the Definite Integral

Absolute Value of a Function in Integration

Integrating the absolute value of a function means summing all areas as positive, regardless of whether the function is above or below the x-axis. This ensures the integral represents total area without cancellation from negative parts, which is crucial when evaluating โˆซโ‚€แถœ |ฦ’(x)| dx.
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Average Value of a Function

Area Interpretation from Graphs

When given a graph, the definite integral corresponds to the area between the curve and the x-axis. Understanding how to read and calculate these areas, especially when the function crosses the axis, helps in evaluating integrals accurately, including those involving absolute values.
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Graphing The Derivative
Related Practice
Textbook Question

Use a substitution of the form u = a๐“ + b to evaluate the following indefinite integrals

โˆซ(eยณหฃ โบยน d๐“

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Textbook Question

Definite integrals Use geometry (not Riemann sums) to evaluate the following definite integrals. Sketch a graph of the integrand, show the region in question, and interpret your result.


 โˆซโ‚€โด ฦ’(๐“) d๐“, where ฦ’(๐“) = {5      if ๐“ โ‰ค 2                                                                                                                                                                                     

                      3๐“ โ€• 1  if ๐“ > 2

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Textbook Question

Average distance on a triangle Consider the right triangle with vertices (0,0) ,(0,b) , and (a,0) , where a > 0 and b > 0. Show that the average vertical distance from points on the ๐“-axis to the hypotenuse is b/2 , for all a > 0 .

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Textbook Question

Approximating displacement The velocity of an object is given by the following functions on a specified interval. Approximate the displacement of the object on this interval by subdividing the interval into n subintervals. Use the left endpoint of each subinterval to compute the height of the rectangles.

v = 2t + 1(m/s), for 0 โ‰ค t โ‰ค 8 ; n = 2

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Textbook Question

Derivatives of integrals Simplify the following expressions.


d/d๐“ โˆซโ‚€หฃ (โˆš1 + tยฒ) dt (Hint: โˆซหฃโ‚‹โ‚“ (โˆš1 + tยฒ) dt = โˆซโฐโ‚‹โ‚“ (โˆš1 + tยฒ) dt + โˆซหฃโ‚‹โ‚“ (โˆš1 + tยฒ) dt ) .

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Textbook Question

Suppose the interval [1, 3] is partitioned into n = 4 subintervals. What is the subinterval length โˆ†๐“? List the grid points xโ‚€ , xโ‚ , xโ‚‚ , xโ‚ƒ and xโ‚„. Which points are used for the left, right, and midpoint Riemann sums?

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