Processing math: 100%
Skip to main content
Library homepage
 

Text Color

Text Size

 

Margin Size

 

Font Type

Enable Dyslexic Font
Mathematics LibreTexts

2.1E: Exercises for Section 6.1

( \newcommand{\kernel}{\mathrm{null}\,}\)

For exercises 1 - 2, determine the area of the region between the two curves in the given figure by integrating over the x-axis.

1) y=x23 and y=1

This figure is has two graphs. They are the functions f(x) = x^2-3and g(x)=1. In between these graphs is a shaded region, bounded above by g(x) and below by f(x). The shaded area is between x=-2 and x=2.

Answer
323units2

2) y=x2 and y=3x+4

This figure is has two graphs. They are the functions f(x) = x^2 and g(x)= 3x+4. In between these graphs is a shaded region, bounded above by g(x) and below by g(x).

For exercises 3 - 4, split the region between the two curves into two smaller regions, then determine the area by integrating over the x-axis. Note that you will have two integrals to solve.

3) y=x3 and y=x2+x

This figure is has two graphs. They are the functions f(x) = x^3 and g(x)= x^2+x. These graphs intersect twice. The regions between the intersections are shaded. The first region is bounded above by f(x) and below by g(x). The second region is bounded above by g(x) and below by f(x).

Answer
1312units2

4) y=cosθ and y=0.5, for 0θπ

This figure is has two graphs. They are the functions f(theta) = cos(theta) and g(x)= 0.5. These graphs intersect twice. The regions between the intersections are shaded. The first region is bounded above by f(x) and below by g(x). The second region is bounded above by g(x) and below by f(x).

For exercises 5-6, determine the area of the region between the two curves by integrating over the y-axis.

5) x=y2 and x=9

This figure is has two graphs. They are the equations x=y^2 and x=9. The region between the graphs is shaded. It is horizontal, between the y-axis and the line x=9.

Answer
36units2

6) y=x and x=y2

This figure is has two graphs. They are the equations y=x and x=y^2. The region between the graphs is shaded, bounded above by x=y^2 and below by y=x.

For exercises 7 - 13, graph the equations and shade the area of the region between the curves. Determine its area by integrating over the x-axis.

7) y=x2 and y=x2+18x

Answer

This figure is has two graphs. They are the functions f(x)=x^2 and g(x)=-x^2+18x. The region between the graphs is shaded, bounded above by g(x) and below by f(x). It is in the first quadrant.

243 square units

8) y=1x,y=1x2, and x=3

9) y=cosx and y=cos2x on x[π,π]

Answer

This figure is has two graphs. They are the functions y=cos(x) and y=cos^2(x). The graphs are periodic and resemble waves. There are four regions created by intersections of the curves. The areas are shaded.

4 square units

10) y=ex,y=e2x1, and x=0

11) y=ex,y=ex,x=1 and x=1

Answer

This figure is has two graphs. They are the functions f(x)=e^x and g(x)=e^-x. There are two shaded regions. In the second quadrant the region is bounded by x=-1, g(x) above and f(x) below. The second region is in the first quadrant and is bounded by f(x) above, g(x) below, and x=1.

2(e1)2eunits2

12) y=e,y=ex, and y=ex

13) y=|x| and y=x2

Answer

This figure is has two graphs. They are the functions f(x)=x^2 and g(x)=absolute value of x. There are two shaded regions. The first region is in the second quadrant and is between g(x) above and f(x) below. The second region is in the first quadrant and is bounded above by g(x) and below by f(x).

13units2

For exercises 14 - 19, graph the equations and shade the area of the region between the curves. If necessary, break the region into sub-regions to determine its entire area.

14) y=sin(πx),y=2x, and x>0

15) y=12x,y=x, and y=1

Answer

This figure is has three graphs. They are the functions f(x)=squareroot of x, y=12-x, and y=1. The region between the graphs is shaded, bounded above and to the left by f(x), above and to the right by the line y=12-x, and below by the line y=1. It is in the first quadrant.

343units2

16) y=sinx and y=cosx over x[π,π]

17) y=x3 and y=x22x over x[1,1]

Answer

This figure is has two graphs. They are the functions f(x)=x^3 and g(x)=x^2-2x. There are two shaded regions between the graphs. The first region is bounded to the left by the line x=-2, above by g(x) and below by f(x). The second region is bounded above by f(x), below by g(x) and to the right by the line x=2.

52units2

18) y=x2+9 and y=10+2x over x[1,3]

19) y=x3+3x and y=4x

Answer

This figure is has two graphs. They are the functions f(x)=x^3+3x and g(x)=4x. There are two shaded regions between the graphs. The first region is bounded above by f(x) and below by g(x). The second region is bounded above by g(x), below by f(x).

12units2

For exercises 20 -25, graph the equations and shade the area of the region between the curves. Determine its area by integrating over the y-axis.

20) x=y3 and x=3y2

21) x=2y and x=y3y

Answer

This figure is has two graphs. They are the equations x=2y and x=y^3-y. The graphs intersect in the third quadrant and again in the first quadrant forming two closed regions in between them.

92units2

22) x=3+y2 and x=yy2

23) y2=x and x=y+2

Answer

This figure is has two graphs. They are the equations x=y+2 and y^2=x. The graphs intersect, forming a region in between them

92units2

24) x=|y| and 2x=y2+2

25) x=siny,x=cos(2y),y=π/2, and y=π/2

Answer

This figure is has two graphs. They are the equations x=cos(y) and x=sin(y). The graphs intersect, forming two regions bounded above by the line y=pi/2 and below by the line y=-pi/2.

332units2

For exercises 26 - 37, graph the equations and shade the area of the region between the curves. Determine its area by integrating over the x-axis or y-axis, whichever seems more convenient.

26) x=y4 and x=y5

27) y=xex,y=ex,x=0, and x=1.

Answer

This figure is has two graphs. They are the equations y=xe^x and y=e^x. The graphs intersect, forming a region in between them in the first quadrant.

(e2)units2

28) y=x6 and y=x4

29) x=y3+2y2+1 and x=y2+1

Answer

Two curves plotted against X and Y axes. One curve is a sideways parabola opening to the left and labeled 'X equals negative Y squared plus 1.' The other curve looks like a horizontally stretched letter S and is labeled 'X equals Y cubed plus 2 Y squared plus 1.' The apex of the parabola touches the upper curve of the S near X equals 1 and Y equals 0. The lower curve of the S also crosses the parabola near X equals negative 8 and Y equals negative 3.

274units2

30) y=|x| and y=x21

31) y=43x and y=1x

Answer

This figure is has two graphs. They are the equations y=4-3x and y=1/x. The graphs intersect, having region between them shaded. The region is in the first quadrant.

(43ln(3))units2

32) y=sinx,x=π/6,x=π/6, and y=cos3x

33) y=x23x+2 and y=x32x2x+2

Answer
This figure is has two graphs. They are the equations y=x^2-3x+2 and y=x^3-2x^2-x+2. The graphs intersect, having region between them shaded.
12
square units

34) y=2cos3(3x),y=1,x=π4, and x=π4

35) y+y3=x and 2y=x

Answer

This figure is has two graphs. They are the equations 2y=x and y+y^3=x. The graphs intersect, forming two regions. The regions are shaded.

12 square units

36) y=1x2 and y=x21

37) y=cos1x,y=sin1x,x=1, and x=1

Answer

This figure is has two graphs. They are the equations y=arccos(x) and y=arcsin (x). The graphs intersect, forming two regions. The first region is bounded to the left by x=-1. The second region is bounded to the right by x=1. Both regions are shaded.

2(2π) square units

For exercises 38 - 47, find the exact area of the region bounded by the given equations if possible. If you are unable to determine the intersection points analytically, use a calculator to approximate the intersection points with three decimal places and determine the approximate area of the region.

38) [T] x=ey and y=x2

39) [T] y=x2 and y=1x2

Answer
1.067 square units

40) [T] y=3x2+8x+9 and 3y=x+24

41) [T] x=4y2 and y2=1+x2

Answer
0.852 square units

42) [T] x2=y3 and x=3y

43) [T] y=sin3x+2,y=tanx,x=1.5, and x=1.5

Answer
7.523 square units

44) [T] y=1x2 and y2=x2

45) [T] y=1x2 and y=x2+2x+1

Answer
3π412 square units

46) [T] x=4y2 and x=1+3y+y2

47) [T] y=cosx,y=ex,x=π, andx=0

Answer
1.429 square units

48) The largest triangle with a base on the x-axis that fits inside the upper half of the unit circle y2+x2=1 is given by y=1+x and y=1x. See the following figure. What is the area inside the semicircle but outside the triangle?

This figure is has the graph of a circle with center at the origin and radius of 1. There is a triangle inscribed with base on the x-axis from -1 to 1 and the third corner at the point y=1.

49) A factory selling cell phones has a marginal cost function C(x)=0.01x23x+229, where x represents the number of cell phones, and a marginal revenue function given by R(x)=4292x. Find the area between the graphs of these curves and x=0. What does this area represent?

Answer
$33,333.33 total profit for 200 cell phones sold

50) An amusement park has a marginal cost function C(x)=1000ex+5, where x represents the number of tickets sold, and a marginal revenue function given by R(x)=600.1x. Find the total profit generated when selling 550 tickets. Use a calculator to determine intersection points, if necessary, to two decimal places.

51) The tortoise versus the hare: The speed of the hare is given by the sinusoidal function H(t)=1cos((πt)/2) whereas the speed of the tortoise is T(t)=(1/2)tan1(t/4), where t is time measured in hours and the speed is measured in miles per hour. Find the area between the curves from time t=0 to the first time after one hour when the tortoise and hare are traveling at the same speed. What does it represent? Use a calculator to determine the intersection points, if necessary, accurate to three decimal places.

Answer
3.263 mi represents how far ahead the hare is from the tortoise

52) The tortoise versus the hare: The speed of the hare is given by the sinusoidal function H(t)=(1/2)(1/2)cos(2πt) whereas the speed of the tortoise is T(t)=t, where t is time measured in hours and speed is measured in kilometers per hour. If the race is over in 1 hour, who won the race and by how much? Use a calculator to determine the intersection points, if necessary, accurate to three decimal places.

For exercises 53 - 55, find the area between the curves by integrating with respect to x and then with respect to y. Is one method easier than the other? Do you obtain the same answer?

53) y=x2+2x+1 and y=x23x+4

Answer
34324 square units

54) y=x4 and x=y5

55) x=y22 and x=2y

Answer
43 square units

For exercises 56 - 57, solve using calculus, then check your answer with geometry.

56) Determine the equations for the sides of the square that touches the unit circle on all four sides, as seen in the following figure. Find the area between the perimeter of this square and the unit circle. Is there another way to solve this without using calculus?

This figure is the graph of a circle centered at the origin with radius of 1. There is a circumscribed square around the circle.

57) Find the area between the perimeter of the unit circle and the triangle created from y=2x+1,y=12x and y=35, as seen in the following figure. Is there a way to solve this without using calculus?

This figure is the graph of a circle centered at the origin with radius of 1. There are three lines intersecting the circle. The lines intersect the circle at three points to form a triangle within the circle.

Answer
(π3225) square units

Contributors

Gilbert Strang (MIT) and Edwin “Jed” Herman (Harvey Mudd) with many contributing authors. This content by OpenStax is licensed with a CC-BY-SA-NC 4.0 license. Download for free at http://cnx.org.


2.1E: Exercises for Section 6.1 is shared under a not declared license and was authored, remixed, and/or curated by LibreTexts.

Support Center

How can we help?