Explain why each of the following integrals is improper. (a) \(\int_{1}^{4} \frac{d x}{x\ -\ 3}\) (b) \(\int_{3}^{\infty} \frac{d x}{x^{2}\ -\ 4}\) (c) \(\int_{0}^{1} \tan \pi x \ d x\) (d) \(\int_{-\infty}^{-1} \frac{e^{x}}{x} \ d x\) Equation Transcription: ? ? ? tan x dx ? dx Text Transcription: integral _1 ^4 dx/x-3 integral _3 ^infinity dx/x^2-4 integral _0 ^1 tan pi x dx integral _-infinity ^-1 e^x/x dx
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Textbook Solutions for Calculus: Early Transcendentals
Question
Astronomers use a technique called stellar stereography to determine the density of stars in a star cluster from the observed (two-dimensional) density that can be analyzed from a photograph. Suppose that in a spherical cluster of radius \(R\) the density of stars depends only on the distance \(r\) from the center of the cluster. If the perceived star density is given by \(y(s)\), where \(s\) is the observed planar distance from the center of the cluster, and \(x(r)\) is the actual density, it can be shown that
\(y(s)=\int_{s}^{R} \frac{2 r}{\sqrt{r^{2}-s^{2}}} x(r) d r\)
If the actual density of stars in a cluster is \(x(r)=\frac{1}{2}(R-r)^{2}\) find the perceived density \(y(s)\).
Solution
The first step in solving 7.8 problem number trying to solve the problem we have to refer to the textbook question: Astronomers use a technique called stellar stereography to determine the density of stars in a star cluster from the observed (two-dimensional) density that can be analyzed from a photograph. Suppose that in a spherical cluster of radius \(R\) the density of stars depends only on the distance \(r\) from the center of the cluster. If the perceived star density is given by \(y(s)\), where \(s\) is the observed planar distance from the center of the cluster, and \(x(r)\) is the actual density, it can be shown that \(y(s)=\int_{s}^{R} \frac{2 r}{\sqrt{r^{2}-s^{2}}} x(r) d r\)If the actual density of stars in a cluster is \(x(r)=\frac{1}{2}(R-r)^{2}\) find the perceived density \(y(s)\).
From the textbook chapter Improper Integrals you will find a few key concepts needed to solve this.
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