Chapter 16: Problem 9
What coordinate system is suggested if the integrand of a triple integral involves \(x^{2}+y^{2} ?\)
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Chapter 16: Problem 9
What coordinate system is suggested if the integrand of a triple integral involves \(x^{2}+y^{2} ?\)
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Improper integrals Improper integrals arise in polar coordinates when the radial coordinate r becomes arbitrarily large. Under certain conditions, these integrals are treated in the usual way: $$\int_{\alpha}^{\beta} \int_{a}^{\infty} g(r, \theta) r d r d \theta=\lim _{b \rightarrow \infty} \int_{\alpha}^{\beta} \int_{a}^{b} g(r, \theta) r d r d \theta$$ Use this technique to evaluate the following integrals. $$\iint_{R} e^{-x^{2}-y^{2}} d A ; R=\left\\{(r, \theta): 0 \leq r<\infty, 0 \leq \theta \leq \frac{\pi}{2}\right\\}$$
Improper integrals Improper integrals arise in polar coordinates when the radial coordinate r becomes arbitrarily large. Under certain conditions, these integrals are treated in the usual way: $$\int_{\alpha}^{\beta} \int_{a}^{\infty} g(r, \theta) r d r d \theta=\lim _{b \rightarrow \infty} \int_{\alpha}^{\beta} \int_{a}^{b} g(r, \theta) r d r d \theta$$ Use this technique to evaluate the following integrals. $$\iint_{R} \frac{d A}{\left(x^{2}+y^{2}\right)^{5 / 2}} ; R=\\{(r, \theta): 1 \leq r<\infty, 0 \leq \theta \leq 2 \pi\\}$$
Determine whether the following statements are true and give an explanation or counterexample. a. A thin plate of constant density that is symmetric about the \(x\) -axis has a center of mass with an \(x\) -coordinate of zero. b. A thin plate of constant density that is symmetric about both the \(x\) -axis and the \(y\) -axis has its center of mass at the origin. c. The center of mass of a thin plate must lie on the plate. d. The center of mass of a connected solid region (all in one piece) must lie within the region.
Mass from density data The following table gives the density (in units of \(\mathrm{g} / \mathrm{cm}^{2}\) ) at selected points (in polar coordinates) of a thin semicircular plate of radius \(3 .\) Estimate the mass of the plate and explain your method. $$\begin{array}{|c|c|c|c|c|c|}\hline & \boldsymbol{\theta}=\mathbf{0} & \boldsymbol{\theta}=\pi / 4 & \boldsymbol{\theta}=\pi / 2 &\boldsymbol{\theta}=3 \pi / 4 & \boldsymbol{\theta}=\pi \\\\\hline r=1 & 2.0 & 2.1 & 2.2 & 2.3 & 2.4 \\\\\hline r=2 & 2.5 & 2.7 & 2.9 & 3.1 & 3.3 \\\\\hline r=3 & 3.2 & 3.4 & 3.5 & 3.6 & 3.7 \\\\\hline\end{array}$$
Evaluate the following integrals using polar coordinates. Assume \((r, \theta)\) are polar coordinates. A sketch is helpful. $$\iint_{R}\left(x^{2}+y^{2}\right) d A ; R=\\{(r, \theta): 0 \leq r \leq 4,0 \leq \theta \leq 2 \pi\\}$$
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