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Let’s revisit the checkpoint associated with [link] , only this time, let’s integrate with respect to y . Let be the region depicted in the following figure. Find the area of R by integrating with respect to y .

This figure is has two graphs in the first quadrant. They are the functions f(x) = squareroot of x and g(x)= 3/2 – x/2. In between these graphs is a shaded region, bounded to the left by f(x) and to the right by g(x). All of which is above the x-axis. The shaded area is between x=0 and x=3.

5 3 units 2

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Key concepts

  • Just as definite integrals can be used to find the area under a curve, they can also be used to find the area between two curves.
  • To find the area between two curves defined by functions, integrate the difference of the functions.
  • If the graphs of the functions cross, or if the region is complex, use the absolute value of the difference of the functions. In this case, it may be necessary to evaluate two or more integrals and add the results to find the area of the region.
  • Sometimes it can be easier to integrate with respect to y to find the area. The principles are the same regardless of which variable is used as the variable of integration.

Key equations

  • Area between two curves, integrating on the x -axis
    A = a b [ f ( x ) g ( x ) ] d x
  • Area between two curves, integrating on the y -axis
    A = c d [ u ( y ) v ( y ) ] d y

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

y = x 2 3 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.

32 3

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For the following exercises, 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.

y = x 3 and y = x 2 + 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).

13 12

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y = cos θ and y = 0.5 , for 0 θ π

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

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

y = x 2 and y = x 2 + 18 x


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

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y = 1 x , y = 1 x 2 , and x = 3

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y = cos x and y = cos 2 x on x = [ π , π ]


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

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y = e x , y = e 2 x 1 , and x = 0

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y = e x , y = e x , x = −1 and x = 1


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 ( e 1 ) 2 e

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y = e , y = e x , and y = e x

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y = | x | and y = x 2


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).
1 3

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For the following exercises, 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.

y = sin ( π x ) , y = 2 x , and x > 0

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y = 12 x , y = x , and y = 1


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.
34 3

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y = sin x and y = cos x over x = [ π , π ]

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y = x 3 and y = x 2 2 x over x = [ −1 , 1 ]


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.
5 2

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y = x 2 + 9 and y = 10 + 2 x over x = [ −1 , 3 ]

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y = x 3 + 3 x and y = 4 x


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).
1 2

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

x = y 3 and x = 3 y 2

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x = 2 y and x = y 3 y


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.
9 2

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x = −3 + y 2 and x = y y 2

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y 2 = x and x = y + 2


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
9 2

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x = | y | and 2 x = y 2 + 2

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x = sin y , x = cos ( 2 y ) , y = π / 2 , and y = π / 2


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.
3 3 2

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For the following exercises, 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.

y = x e x , y = e x , x = 0 , and x = 1


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.
e −2

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x = y 3 + 2 y 2 + 1 and x = y 2 + 1


This figure is has two graphs. They are the equations x=-y^2+1 and x=y^3+2y^2. The graphs intersect, forming two regions in between them.
27 4

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y = | x | and y = x 2 1

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y = 4 3 x and y = 1 x


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.
4 3 ln ( 3 )

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y = sin x , x = π / 6 , x = π / 6 , and y = cos 3 x

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y = x 2 3 x + 2 and y = x 3 2 x 2 x + 2


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.
1 2

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y = 2 cos 3 ( 3 x ) , y = −1 , x = π 4 , and x = π 4

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y + y 3 = x and 2 y = x


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.
1 2

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y = 1 x 2 and y = x 2 1

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y = cos −1 x , y = sin −1 x , x = −1 , and x = 1


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 ( 2 π )

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For the following exercises, 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.

[T] x = e y and y = x 2

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[T] y = x 2 and y = 1 x 2

1.067

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[T] y = 3 x 2 + 8 x + 9 and 3 y = x + 24

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[T] x = 4 y 2 and y 2 = 1 + x 2

0.852

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[T] x 2 = y 3 and x = 3 y

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[T] y = sin 3 x + 2 , y = tan x , x = −1.5 , and x = 1.5

7.523

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[T] y = 1 x 2 and y 2 = x 2

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[T] y = 1 x 2 and y = x 2 + 2 x + 1

3 π 4 12

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[T] x = 4 y 2 and x = 1 + 3 y + y 2

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[T] y = cos x , y = e x , x = π , and x = 0

1.429

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The largest triangle with a base on the x -axis that fits inside the upper half of the unit circle y 2 + x 2 = 1 is given by y = 1 + x and y = 1 x . 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.
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A factory selling cell phones has a marginal cost function C ( x ) = 0.01 x 2 3 x + 229 , where x represents the number of cell phones, and a marginal revenue function given by R ( x ) = 429 2 x . Find the area between the graphs of these curves and x = 0 . What does this area represent?

$ 33,333.33 total profit for 200 cell phones sold

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An amusement park has a marginal cost function C ( x ) = 1000 e x + 5 , where x represents the number of tickets sold, and a marginal revenue function given by R ( x ) = 60 0.1 x . Find the total profit generated when selling 550 tickets. Use a calculator to determine intersection points, if necessary, to two decimal places.

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The tortoise versus the hare: The speed of the hare is given by the sinusoidal function H ( t ) = 1 cos ( ( π t ) / 2 ) whereas the speed of the tortoise is T ( t ) = ( 1 / 2 ) tan −1 ( 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.

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

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The tortoise versus the hare: The speed of the hare is given by the sinusoidal function H ( t ) = ( 1 / 2 ) ( 1 / 2 ) cos ( 2 π t ) 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.

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For the following exercises, 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?

y = x 2 + 2 x + 1 and y = x 2 3 x + 4

343 24

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x = y 2 2 and x = 2 y

4 3

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For the following exercises, solve using calculus, then check your answer with geometry.

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.
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Find the area between the perimeter of the unit circle and the triangle created from y = 2 x + 1 , y = 1 2 x and y = 3 5 , 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.

π 32 25

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Questions & Answers

What are the factors that affect demand for a commodity
Florence Reply
differentiate between demand and supply giving examples
Lambiv Reply
differentiated between demand and supply using examples
Lambiv
what is labour ?
Lambiv
how will I do?
Venny Reply
how is the graph works?I don't fully understand
Rezat Reply
information
Eliyee
devaluation
Eliyee
t
WARKISA
hi guys good evening to all
Lambiv
multiple choice question
Aster Reply
appreciation
Eliyee
explain perfect market
Lindiwe Reply
In economics, a perfect market refers to a theoretical construct where all participants have perfect information, goods are homogenous, there are no barriers to entry or exit, and prices are determined solely by supply and demand. It's an idealized model used for analysis,
Ezea
What is ceteris paribus?
Shukri Reply
other things being equal
AI-Robot
When MP₁ becomes negative, TP start to decline. Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of lab
Kelo
Extuples Suppose that the short-run production function of certain cut-flower firm is given by: Q=4KL-0.6K2 - 0.112 • Where is quantity of cut flower produced, I is labour input and K is fixed capital input (K-5). Determine the average product of labour (APL) and marginal product of labour (MPL)
Kelo
yes,thank you
Shukri
Can I ask you other question?
Shukri
what is monopoly mean?
Habtamu Reply
What is different between quantity demand and demand?
Shukri Reply
Quantity demanded refers to the specific amount of a good or service that consumers are willing and able to purchase at a give price and within a specific time period. Demand, on the other hand, is a broader concept that encompasses the entire relationship between price and quantity demanded
Ezea
ok
Shukri
how do you save a country economic situation when it's falling apart
Lilia Reply
what is the difference between economic growth and development
Fiker Reply
Economic growth as an increase in the production and consumption of goods and services within an economy.but Economic development as a broader concept that encompasses not only economic growth but also social & human well being.
Shukri
production function means
Jabir
What do you think is more important to focus on when considering inequality ?
Abdisa Reply
any question about economics?
Awais Reply
sir...I just want to ask one question... Define the term contract curve? if you are free please help me to find this answer 🙏
Asui
it is a curve that we get after connecting the pareto optimal combinations of two consumers after their mutually beneficial trade offs
Awais
thank you so much 👍 sir
Asui
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities, where neither p
Cornelius
In economics, the contract curve refers to the set of points in an Edgeworth box diagram where both parties involved in a trade cannot be made better off without making one of them worse off. It represents the Pareto efficient allocations of goods between two individuals or entities,
Cornelius
Suppose a consumer consuming two commodities X and Y has The following utility function u=X0.4 Y0.6. If the price of the X and Y are 2 and 3 respectively and income Constraint is birr 50. A,Calculate quantities of x and y which maximize utility. B,Calculate value of Lagrange multiplier. C,Calculate quantities of X and Y consumed with a given price. D,alculate optimum level of output .
Feyisa Reply
Answer
Feyisa
c
Jabir
the market for lemon has 10 potential consumers, each having an individual demand curve p=101-10Qi, where p is price in dollar's per cup and Qi is the number of cups demanded per week by the i th consumer.Find the market demand curve using algebra. Draw an individual demand curve and the market dema
Gsbwnw Reply
suppose the production function is given by ( L, K)=L¼K¾.assuming capital is fixed find APL and MPL. consider the following short run production function:Q=6L²-0.4L³ a) find the value of L that maximizes output b)find the value of L that maximizes marginal product
Abdureman
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Source:  OpenStax, Calculus volume 1. OpenStax CNX. Feb 05, 2016 Download for free at http://cnx.org/content/col11964/1.2
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