Multi-Part Free Response with Area, Volume, and Additional Calculus
Free-response question where finding the area between curves is one part, combined with additional parts such as computing volumes of revolution, volumes with known cross sections, related rates, or optimization.
Let $R$ be the region bounded by the graph of $y = e ^ { 2 x - x ^ { 2 } }$ and the horizontal line $y = 2$, and let $S$ be the region bounded by the graph of $y = e ^ { 2 x - x ^ { 2 } }$ and the horizontal lines $y = 1$ and $y = 2$, as shown above. (a) Find the area of $R$. (b) Find the area of $S$. (c) Write, but do not evaluate, an integral expression that gives the volume of the solid generated when $R$ is rotated about the horizontal line $y = 1$.
Let $R$ be the region bounded by the graphs of $y = \sin ( \pi x )$ and $y = x ^ { 3 } - 4 x$, as shown in the figure above. (a) Find the area of $R$. (b) The horizontal line $y = - 2$ splits the region $R$ into two parts. Write, but do not evaluate, an integral expression for the area of the part of $R$ that is below this horizontal line. (c) The region $R$ is the base of a solid. For this solid, each cross section perpendicular to the $x$-axis is a square. Find the volume of this solid. (d) The region $R$ models the surface of a small pond. At all points in $R$ at a distance $x$ from the $y$-axis, the depth of the water is given by $h ( x ) = 3 - x$. Find the volume of water in the pond.
Let $R$ be the region in the first quadrant bounded by the $x$-axis and the graphs of $y = \ln x$ and $y = 5 - x$, as shown in the figure above. (a) Find the area of $R$. (b) Region $R$ is the base of a solid. For the solid, each cross section perpendicular to the $x$-axis is a square. Write, but do not evaluate, an expression involving one or more integrals that gives the volume of the solid. (c) The horizontal line $y = k$ divides $R$ into two regions of equal area. Write, but do not solve, an equation involving one or more integrals whose solution gives the value of $k$.
The functions $f$ and $g$ are given by $f ( x ) = \sqrt { x }$ and $g ( x ) = 6 - x$. Let $R$ be the region bounded by the $x$-axis and the graphs of $f$ and $g$, as shown in the figure above. (a) Find the area of $R$. (b) The region $R$ is the base of a solid. For each $y$, where $0 \leq y \leq 2$, the cross section of the solid taken perpendicular to the $y$-axis is a rectangle whose base lies in $R$ and whose height is $2 y$. Write, but do not evaluate, an integral expression that gives the volume of the solid. (c) There is a point $P$ on the graph of $f$ at which the line tangent to the graph of $f$ is perpendicular to the graph of $g$. Find the coordinates of point $P$.
Let $R$ be the shaded region bounded by the graph of $y = x e ^ { x ^ { 2 } }$, the line $y = - 2 x$, and the vertical line $x = 1$, as shown in the figure above. (a) Find the area of $R$. (b) Write, but do not evaluate, an integral expression that gives the volume of the solid generated when $R$ is rotated about the horizontal line $y = - 2$. (c) Write, but do not evaluate, an expression involving one or more integrals that gives the perimeter of $R$.
The graphs of the functions $f$ and $g$ are shown in the figure for $0 \leq x \leq 3$. It is known that $g(x) = \frac{12}{3 + x}$ for $x \geq 0$. The twice-differentiable function $f$, which is not explicitly given, satisfies $f(3) = 2$ and $\int_{0}^{3} f(x)\, dx = 10$. (a) Find the area of the shaded region enclosed by the graphs of $f$ and $g$. (b) Evaluate the improper integral $\int_{0}^{\infty} (g(x))^{2}\, dx$, or show that the integral diverges. (c) Let $h$ be the function defined by $h(x) = x \cdot f'(x)$. Find the value of $\int_{0}^{3} h(x)\, dx$.
An advertiser wishes to print a logo on a T-shirt. He draws this logo using the curves of two functions $f$ and $g$ defined on $\mathbb{R}$ by: $$f(x) = \mathrm{e}^{-x}(-\cos x + \sin x + 1) \text{ and } g(x) = -\mathrm{e}^{-x}\cos x$$ It is admitted that the functions $f$ and $g$ are differentiable on $\mathbb{R}$.
Part A — Study of function $f$
Justify that, for all $x \in \mathbb{R}$: $$-\mathrm{e}^{-x} \leqslant f(x) \leqslant 3\mathrm{e}^{-x}$$
Deduce the limit of $f$ as $x \to +\infty$.
Prove that, for all $x \in \mathbb{R}$, $f'(x) = \mathrm{e}^{-x}(2\cos x - 1)$ where $f'$ is the derivative of $f$.
In this question, we study function $f$ on the interval $[-\pi; \pi]$. a. Determine the sign of $f'(x)$ for $x$ in the interval $[-\pi; \pi]$. b. Deduce the variations of $f$ on $[-\pi; \pi]$.
Part B — Area of the logo
We denote by $\mathscr{C}_f$ and $\mathscr{C}_g$ the graphs of functions $f$ and $g$ in an orthonormal coordinate system $(\mathrm{O}; \vec{\imath}, \vec{\jmath})$. The graphical unit is 2 centimetres.
Study the relative position of curve $\mathscr{C}_f$ with respect to curve $\mathscr{C}_g$ on $\mathbb{R}$.
Let $H$ be the function defined on $\mathbb{R}$ by: $$H(x) = \left(-\frac{\cos x}{2} - \frac{\sin x}{2} - 1\right)\mathrm{e}^{-x}$$ It is admitted that $H$ is an antiderivative of the function $x \mapsto (\sin x + 1)\mathrm{e}^{-x}$ on $\mathbb{R}$. We denote by $\mathscr{D}$ the region bounded by curve $\mathscr{C}_f$, curve $\mathscr{C}_g$ and the lines with equations $x = -\frac{\pi}{2}$ and $x = \frac{3\pi}{2}$. a. Shade the region $\mathscr{D}$ on the graph in the appendix to be returned with your work. b. Calculate, in square units, the area of region $\mathscr{D}$, then give an approximate value to $10^{-2}$ in $\mathrm{cm}^2$.
The derivative $f'(x)$ of a function $f(x)$ that is differentiable on the set of all real numbers is $$f'(x) = -x + e^{1 - x^{2}}$$ For a positive number $t$, let $g(t)$ be the area of the region enclosed by the tangent line to the curve $y = f(x)$ at the point $(t, f(t))$, the curve $y = f(x)$, and the $y$-axis. What is the value of $g(1) + g'(1)$? [4 points] (1) $\frac{1}{2}e + \frac{1}{2}$ (2) $\frac{1}{2}e + \frac{2}{3}$ (3) $\frac{1}{2}e + \frac{5}{6}$ (4) $\frac{2}{3}e + \frac{1}{2}$ (5) $\frac{2}{3}e + \frac{2}{3}$
Given the functions $$f ( x ) = 2 + 2 x - 2 x ^ { 2 } \text { and } g ( x ) = 2 - 6 x + 4 x ^ { 2 } + 2 x ^ { 3 } ,$$ find:\ a) (1 point) Study the differentiability of $h ( x ) = | f ( x ) |$.\ b) (1.5 points) Find the area of the region bounded by the curves\ $y = f ( x ) , y = g ( x ) , x = 0$ and $x = 2$.
On the coordinate plane, let $\Gamma$ denote the graph of the polynomial function $y = x ^ { 3 } - 4 x ^ { 2 } + 5 x$ , and let $L$ denote the line $y = m x$ , where $m$ is a real number. Based on the above, answer the following questions. (1) When $m = 2$ , find the $x$-coordinates of the three distinct intersection points of $\Gamma$ and $L$ in the range $x \geq 0$ . (2 points) (2) Based on (1), find the area of the bounded region enclosed by $\Gamma$ and $L$ . (4 points) (3) In the range $x \geq 0$ , if $\Gamma$ and $L$ have three distinct intersection points, then the maximum range of $m$ satisfying this condition is $a < m < b$ . Find the values of $a$ and $b$ . (6 points)