Chapter 6: Problem 4
How are the derivative formulas for the hyperbolic functions and the trigonometric functions alike? How are they different?
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Chapter 6: Problem 4
How are the derivative formulas for the hyperbolic functions and the trigonometric functions alike? How are they different?
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The burning of fossil fuels releases greenhouse gases (roughly \(60 \% \text { carbon dioxide })\) into the atmosphere. In 2010 , the United States released approximately 5.8 billion metric tons of carbon dioxide (Environmental Protection Agency estimate), while China released approximately 8.2 billion metric tons (U.S. Department of Energy estimate). Reasonable estimates of the growth rate in carbon dioxide emissions are \(4 \%\) per year for the United States and \(9 \%\) per year for China. In 2010 , the U.S. population was 309 million, growing at a rate of \(0.7 \%\) per year, and the population of China was 1.3 billion, growing at a rate of \(0.5 \%\) per year. a. Find exponential growth functions for the amount of carbon dioxide released by the United States and China. Let \(t=0\) correspond to 2010 . b. According to the models in part (a), when will Chinese emissions double those of the United States? c. What was the amount of carbon dioxide released by the United States and China per capita in \(2010 ?\) d. Find exponential growth functions for the per capita amount of carbon dioxide released by the United States and China. Let \(t=0\) correspond to 2010. e. Use the models of part (d) to determine the year in which per capita emissions in the two countries are equal.
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, then they differ by an additive constant. Set \(x=1\) to evaluate the constant and prove that \(\ln x y=\ln x+\ln y\).
Consider the parabola \(y=x^{2} .\) Let \(P, Q,\) and \(R\) be points on the parabola with \(R\) between \(P\) and \(Q\) on the curve. Let \(\ell_{p}, \ell_{Q},\) and \(\ell_{R}\) be the lines tangent to the parabola at \(P, Q,\) and \(R,\) respectively (see figure). Let \(P^{\prime}\) be the intersection point of \(\ell_{Q}\) and \(\ell_{R},\) let \(Q^{\prime}\) be the intersection point of \(\ell_{P}\) and \(\ell_{R},\) and let \(R^{\prime}\) be the intersection point of \(\ell_{P}\) and \(\ell_{Q} .\) Prove that Area \(\Delta P Q R=2 \cdot\) Area \(\Delta P^{\prime} Q^{\prime} R^{\prime}\) in the following cases. (In fact, the property holds for any three points on any parabola.) (Source: Mathematics Magazine 81, 2, Apr 2008) a. \(P\left(-a, a^{2}\right), Q\left(a, a^{2}\right),\) and \(R(0,0),\) where \(a\) is a positive real number b. \(P\left(-a, a^{2}\right), Q\left(b, b^{2}\right),\) and \(R(0,0),\) where \(a\) and \(b\) are positive real numbers c. \(P\left(-a, a^{2}\right), Q\left(b, b^{2}\right),\) and \(R\) is any point between \(P\) and \(Q\) on the curve
Use the inverse relations between \(\ln x\) and \(e^{x}(\exp (x)),\) and the properties of \(\ln x\) to prove the following properties. a. \(\exp (0)=1\) b. \(\exp (x-y)=\frac{\exp (x)}{\exp (y)}\) c. \((\exp (x))^{p}=\exp (p x), p\) rational
Prove that the doubling time for an exponentially increasing quantity is constant for all time.
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