Chapter 14: Problem 21
Find the volume of the solid that lies below the surface \(z=f(x, y)\) and above the region in the \(x y\) -plane bounded by the given curves. $$z=x^{2}+y^{2} ; x=0, x=1, y=0, y=2$$
Short Answer
Expert verified
The volume is \(\frac{10}{3}.\)
Step by step solution
01
Understand the Problem
We have a surface described by the equation \(z = x^2 + y^2\) and a region in the \(xy\)-plane that is defined by the boundaries \(x=0\), \(x=1\), \(y=0\), and \(y=2\). We need to find the volume enclosed by this surface and the \(xy\)-region.
02
Set Up the Double Integral
To find the volume under the surface \(z = x^2 + y^2\) and above the specified region, we will set up a double integral: \(\int_{0}^{1} \int_{0}^{2} (x^2 + y^2)\, dy \, dx.\) Here, the outer integral corresponds to \(x\) from 0 to 1, and the inner integral corresponds to \(y\) from 0 to 2.
03
Integrate with Respect to y
Compute the inner integral by integrating \(x^2 + y^2\) with respect to \(y\): \(\int_{0}^{2} (x^2 + y^2) \, dy.\)This results in: \(x^2y + \frac{y^3}{3}\) evaluated from \(y = 0\) to \(y = 2\).
04
Evaluate the y-Integral
Substitute the limits into the integrated function: \(\left(x^2(2) + \frac{2^3}{3} \right) - \left(x^2(0) + \frac{0^3}{3} \right) = 2x^2 + \frac{8}{3}.\)
05
Integrate with Respect to x
Compute the outer integral, \(\int_{0}^{1} \left( 2x^2 + \frac{8}{3} \right) \, dx.\)This gives: \(\frac{2}{3}x^3 + \frac{8}{3}x\) evaluated from \(x = 0\) to \(x = 1\).
06
Evaluate the x-Integral
Substitute the limits into the integrated function:\(\left(\frac{2}{3}(1)^3 + \frac{8}{3}(1) \right) - \left(\frac{2}{3}(0)^3 + \frac{8}{3}(0) \right) = \frac{2}{3} + \frac{8}{3} = \frac{10}{3}.\)
07
Conclusion
The final result represents the volume of the solid: \(\frac{10}{3}.\)
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Volume Under Surface
In mathematics, finding the volume under a surface is a common task that involves using integration to calculate how much space is enclosed between a surface and a region on a plane beneath it. In this exercise, the surface is defined by the equation \(z = x^2 + y^2\). The goal is to determine the three-dimensional volume between this surface and the rectangular region on the \(xy\)-plane, which is defined by specific boundaries.
- Surface Equation: The surface, \(z\), is determined by the function \(f(x,y) = x^2 + y^2\).
- Region Boundaries: These are the limits within which we are interested in calculating the volume: \(x\) ranges from 0 to 1, and \(y\) ranges from 0 to 2.
Bounded Regions
Bounded regions in calculus refer to specific areas on a plane where variables are constrained within certain limits. For double integrals, the bounded region determines where the function will be evaluated.
- x-boundaries: From \(x = 0\) to \(x = 1\).
- y-boundaries: From \(y = 0\) to \(y = 2\).
Multivariable Calculus
In multivariable calculus, we extend calculus concepts to functions of more than one variable. Here, instead of dealing with a well-defined line or curve, we engage with surfaces and the quantity of space they encompass.
- Functions of Two Variables: The given function, \(f(x, y) = x^2 + y^2\), is a function of two variables, \(x\) and \(y\).
- 3D Space: This moves our focus from curves in 2D to surfaces in 3D, providing a richer set of tools for analysis.
Integration Techniques
Integration techniques are fundamental in dealing with double integrals involving multiple steps, such as integrating a function over a specified region.
- Set Up the Integral: Begin with setting up a double integral: \(\int_{0}^{1} \int_{0}^{2} (x^2 + y^2)\, dy \, dx\).
- Integrate Respect to \(y\): First, integrate the inner integral with respect to \(y\): \(\int_{0}^{2} (x^2 + y^2) \, dy\).
- Integrate Respect to \(x\): Then, integrate the resulting expression with respect to \(x\).
- Evaluating Definite Integrals: Each integration step is followed by applying the limits, yielding a specific numeric result.