Chapter 7: Problem 41
Evaluate the following integrals or state that they diverge. $$\int_{0}^{1} \frac{e^{\sqrt{x}}}{\sqrt{x}} d x$$
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Chapter 7: Problem 41
Evaluate the following integrals or state that they diverge. $$\int_{0}^{1} \frac{e^{\sqrt{x}}}{\sqrt{x}} d x$$
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The reaction of chemical compounds can often be modeled by differential equations. Let \(y(t)\) be the concentration of a substance in reaction for \(t \geq 0\) (typical units of \(y\) are moles/L). The change in the concentration of the substance, under appropriate conditions, is \(\frac{d y}{d t}=-k y^{n},\) where \(k>0\) is a rate constant and the positive integer \(n\) is the order of the reaction. a. Show that for a first-order reaction \((n=1),\) the concentration obeys an exponential decay law. b. Solve the initial value problem for a second-order reaction \((n=2)\) assuming \(y(0)=y_{0}\). c. Graph and compare the concentration for a first-order and second-order reaction with \(k=0.1\) and \(y_{0}=1\).
Three cars, \(A, B,\) and \(C,\) start from rest and accelerate along a line according to the following velocity functions: $$ v_{A}(t)=\frac{88 t}{t+1}, \quad v_{B}(t)=\frac{88 t^{2}}{(t+1)^{2}}, \quad \text { and } \quad v_{C}(t)=\frac{88 t^{2}}{t^{2}+1} $$ a. Which car travels farthest on the interval \(0 \leq t \leq 1 ?\) b. Which car travels farthest on the interval \(0 \leq t \leq 5 ?\) c. Find the position functions for each car assuming that each car starts at the origin. d. Which car ultimately gains the lead and remains in front?
The Eiffel Tower property Let \(R\) be the region between the curves \(y=e^{-\alpha x}\) and \(y=-e^{-\alpha x}\) on the interval \([a, \infty),\) where \(a \geq 0\) and \(c>0 .\) The center of mass of \(R\) is located at \((\bar{x}, 0)\) where \(\bar{x}=\frac{\int_{a}^{\infty} x e^{-c x} d x}{\int_{a}^{\infty} e^{-c x} d x} .\) (The profile of the Eiffel Tower is modeled by the two exponential curves; see the Guided Project The exponential Eiffel Tower.) a. For \(a=0\) and \(c=2,\) sketch the curves that define \(R\) and find the center of mass of \(R\). Indicate the location of the center of mass. b. With \(a=0\) and \(c=2,\) find equations of the lines tangent to the curves at the points corresponding to \(x=0\) c. Show that the tangent lines intersect at the center of mass. d. Show that this same property holds for any \(a \geq 0\) and any \(c>0 ;\) that is, the tangent lines to the curves \(y=\pm e^{-c x}\) at \(x=a\) intersect at the center of mass of \(R\).
Powers of sine and cosine It can be shown that \(\int_{0}^{\pi / 2} \sin ^{n} x d x=\int_{0}^{\pi / 2} \cos ^{n} x d x=\) \(\left\\{\begin{array}{ll}\frac{1 \cdot 3 \cdot 5 \cdots(n-1)}{2 \cdot 4 \cdot 6 \cdots n} \cdot \frac{\pi}{2} & \text { if } n \geq 2 \text { is an even integer } \\ \frac{2 \cdot 4 \cdot 6 \cdots(n-1)}{3 \cdot 5 \cdot 7 \cdots n} & \text { if } n \geq 3 \text { is an odd integer. }\end{array}\right.\)
Use symmetry to evaluate the following integrals. a. \(\int_{-\infty}^{\infty} e^{-|x|} d x\) b. \(\int_{-\infty}^{\infty} \frac{x^{3}}{1+x^{8}} d x\)
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