Chapter 6: Problem 14
Find the area of the surface generated when the given curve is revolved about the \(x\) -axis. $$y=\sqrt{5 x-x^{2}} \text { on }[1,4]$$
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Chapter 6: Problem 14
Find the area of the surface generated when the given curve is revolved about the \(x\) -axis. $$y=\sqrt{5 x-x^{2}} \text { on }[1,4]$$
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Carry out the following steps to derive the formula \(\int \operatorname{csch} x d x=\ln |\tanh (x / 2)|+C\) (Theorem 9). a. Change variables with the substitution \(u=x / 2\) to show that $$\int \operatorname{csch} x d x=\int \frac{2 d u}{\sinh 2 u}$$. b. Use the identity for \(\sinh 2 u\) to show that \(\frac{2}{\sinh 2 u}=\frac{\operatorname{sech}^{2} u}{\tanh u}\). c. Change variables again to determine \(\int \frac{\operatorname{sech}^{2} u}{\tanh u} d u,\) and then express your answer in terms of \(x\).
Two bars of length \(L\) have densities \(\rho_{1}(x)=4 e^{-x}\) and \(\rho_{2}(x)=6 e^{-2 x},\) for \(0 \leq x \leq L\) a. For what values of \(L\) is bar 1 heavier than bar \(2 ?\) b. As the lengths of the bars increase, do their masses increase without bound? Explain.
Determine whether the following statements are true and give an explanation or counterexample. a. \(\frac{d}{d x}(\sinh \ln 3)=\frac{\cosh \ln 3}{3}\) b. \(\frac{d}{d x}(\sinh x)=\cosh x\) and \(\frac{d}{d x}(\cosh x)=-\sinh x\) c. Differentiating the velocity equation for an ocean wave \(v=\sqrt{\frac{g \lambda}{2 \pi} \tanh \left(\frac{2 \pi d}{\lambda}\right)}\) results in the acceleration of the wave. d. \(\ln (1+\sqrt{2})=-\ln (-1+\sqrt{2})\) e. \(\int_{0}^{1} \frac{d x}{4-x^{2}}=\frac{1}{2}\left(\operatorname{coth}^{-1} \frac{1}{2}-\operatorname{coth}^{-1} 0\right)\)
A glass has circular cross sections that taper (linearly) from a radius of \(5 \mathrm{cm}\) at the top of the glass to a radius of \(4 \mathrm{cm}\) at the bottom. The glass is \(15 \mathrm{cm}\) high and full of orange juice. How much work is required to drink all the juice through a straw if your mouth is \(5 \mathrm{cm}\) above the top of the glass? Assume the density of orange juice equals the density of water.
Alternative proof of product property Assume that \(y>0\) is fixed and that \(x>0 .\) Show that \(\frac{d}{d x}(\ln x y)=\frac{d}{d x}(\ln x) .\) Recall that if two functions have the same derivative, they differ by an additive constant. Set \(x=1\) to evaluate the constant and prove that \(\ln x y=\ln x+\ln y.\)
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