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Ch. 5 - Integration
Briggs - Calculus: Early Transcendentals 3rd Edition
Briggs3rd EditionCalculus: Early TranscendentalsISBN: 9780136847243Non è quello che usi tu?Cambia libro di testo
Capitolo 5, Problema 5.R.99b

(b) Find the average value of ƒ shown in the figure on the interval [2,6] and then find the point(s) c in (2, 6) guaranteed to exist by the Mean Value Theorem for Integrals. 
Graph of a function f(x) with a peak at (4,5) on the interval [2,6], showing axes labeled x and y.

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Identify the function \( f(x) \) from the graph on the interval \([2,6]\). The graph shows a triangular shape with a peak at \( (4,5) \), increasing linearly from \( (2,1) \) to \( (4,5) \), then decreasing linearly from \( (4,5) \) to \( (6,1) \).
To find the average value of \( f \) on \([2,6]\), use the formula for the average value of a function: \[\text{Average value} = \frac{1}{6-2} \int_2^6 f(x) \, dx = \frac{1}{4} \int_2^6 f(x) \, dx.\]
Calculate the integral \( \int_2^6 f(x) \, dx \) by finding the area under the curve. Since the graph forms a triangle with base length \(6 - 2 = 4\) and height \(5 - 1 = 4\), the area is \[\text{Area} = \frac{1}{2} \times \text{base} \times \text{height} = \frac{1}{2} \times 4 \times 4.\]
Use the area found as the value of the integral \( \int_2^6 f(x) \, dx \), then substitute it back into the average value formula to express the average value of \( f \) on \([2,6]\).
Apply the Mean Value Theorem for Integrals, which guarantees at least one point \( c \in (2,6) \) such that \[f(c) = \text{Average value of } f \text{ on } [2,6].\] Find \( c \) by solving the equation \( f(c) = \text{average value} \) using the piecewise linear definition of \( f(x) \) from the graph.

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