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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 5.2.61

Definite integrals from graphs The figure shows the areas of regions bounded by the graph of Ζ’ and the 𝓍-axis. Evaluate the following integrals.




βˆ«β‚αΆœ Ζ’(𝓍) d𝓍

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1
Identify the points a and c on the x-axis from the graph, which define the limits of integration for the integral \( \int_{a}^{c} f(x) \, dx \).
Observe the graph of \( f(x) \) between \( x = a \) and \( x = c \) and note the areas bounded by the curve and the x-axis. Pay attention to whether the graph is above or below the x-axis in each region, as this affects the sign of the integral.
Calculate the area of each region between the curve and the x-axis separately. If the graph is above the x-axis, the area contributes positively to the integral; if below, it contributes negatively.
Sum the signed areas of all regions between \( a \) and \( c \) to find the value of the definite integral \( \int_{a}^{c} f(x) \, dx \).
Express the final integral as the algebraic sum of these areas, which represents the net area between the curve and the x-axis over the interval \( [a, c] \).

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Key Concepts

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

Definite Integral as Net Area

A definite integral represents the net area between the graph of a function and the x-axis over a given interval. Areas above the x-axis contribute positively, while areas below contribute negatively, affecting the integral's value.
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Interpreting Graphical Areas

When evaluating integrals from graphs, it is essential to identify and measure the areas of regions bounded by the curve and the x-axis. Understanding which parts lie above or below the axis helps determine the sign and magnitude of each area.
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Finding Area When Bounds Are Not Given

Properties of Definite Integrals

Definite integrals are additive over adjacent intervals, meaning the integral from a to c can be split into integrals over subintervals. This property allows summing individual areas to find the total integral value.
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Definition of the Definite Integral
Related Practice
Textbook Question

Max/min of area functions Suppose Ζ’ is continuous on [0 ,∞) and A(𝓍) is the net area of the region bounded by the graph of Ζ’ and the t-axis on [0, x]. Show that the local maxima and minima of A occur at the zeros of Ζ’. Verify this fact with the function Ζ’(𝓍) = 𝓍² - 10𝓍.

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Textbook Question

Suppose an object moves along a line at 15 m/s, for 0 ≀ t < 2 and at 25 m/s, for 2 ≀ t ≀ 5, where t is measured in seconds. Sketch the graph of the velocity function and find the displacement of the object for 0 ≀ t ≀ 5.

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Textbook Question

Explain why βˆ«β‚α΅‡ Ζ’ β€²(𝓍) d𝓍 = Ζ’(b) ― Ζ’(a)

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Textbook Question

Average velocity The velocity in m/s of an object moving along a line over the time interval [0,6] is v (t) = tΒ² + 3t. Find the average velocity of the object over this time interval.

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Textbook Question

A midpoint Riemann sum Approximate the area of the region bounded by the graph of Ζ’(𝓍) = 100 ― xΒ² and the x-axis on [0, 10] with n = 5 subintervals. Use the midpoint of each subinterval to determine the height of each rectangle (see figure).

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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.                                                                                  

                                                                                                                                                                    

 βˆ« 𝓍³ (𝓍⁴ + 16)⁢ d𝓍

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