<< Chapter < Page Chapter >> Page >

Key concepts

  • Parametric equations provide a convenient way to describe a curve. A parameter can represent time or some other meaningful quantity.
  • It is often possible to eliminate the parameter in a parameterized curve to obtain a function or relation describing that curve.
  • There is always more than one way to parameterize a curve.
  • Parametric equations can describe complicated curves that are difficult or perhaps impossible to describe using rectangular coordinates.

For the following exercises, sketch the curves below by eliminating the parameter t . Give the orientation of the curve.

x = t 2 + 2 t , y = t + 1


A parabola open to the right with (−1, 0) being the point furthest the left with arrow going from the bottom through (−1, 0) and up.
orientation: bottom to top

Got questions? Get instant answers now!

x = cos ( t ) , y = sin ( t ) , ( 0 , 2 π ]

Got questions? Get instant answers now!

x = 2 t + 4 , y = t 1


A straight line passing through (0, −3) and (6, 0) with arrow pointing up and to the right.
orientation: left to right

Got questions? Get instant answers now!

x = 3 t , y = 2 t 3 , 1.5 t 3

Got questions? Get instant answers now!

For the following exercises, eliminate the parameter and sketch the graphs.

x = 2 t 2 , y = t 4 + 1

y = x 2 4 + 1
Half a parabola starting at the origin and passing through (2, 2) with arrow pointed up and to the right.

Got questions? Get instant answers now!

For the following exercises, use technology (CAS or calculator) to sketch the parametric equations.

[T] x = t 2 + t , y = t 2 1

Got questions? Get instant answers now!

[T] x = e t , y = e 2 t 1


A curve going through (1, 0) and (0, 3) with arrow pointing up and to the left.

Got questions? Get instant answers now!

[T] x = 3 cos t , y = 4 sin t

Got questions? Get instant answers now!

[T] x = sec t , y = cos t


A graph with asymptotes at the x and y axes. There is a portion of the graph in the third quadrant with arrow pointing down and to the right. There is a portion of the graph in the first quadrant with arrow pointing down and to the right.

Got questions? Get instant answers now!

For the following exercises, sketch the parametric equations by eliminating the parameter. Indicate any asymptotes of the graph.

x = 6 sin ( 2 θ ) , y = 4 cos ( 2 θ )


An ellipse with minor axis vertical and of length 8 and major axis horizontal and of length 12 that is centered at the origin. The arrows go counterclockwise.

Got questions? Get instant answers now!

x = cos θ , y = 2 sin ( 2 θ )

Got questions? Get instant answers now!

x = 3 2 cos θ , y = −5 + 3 sin θ


An ellipse in the fourth quadrant with minor axis horizontal and of length 4 and major axis vertical and of length 6. The arrows go clockwise.

Got questions? Get instant answers now!

x = 4 + 2 cos θ , y = −1 + sin θ

Got questions? Get instant answers now!

x = sec t , y = tan t


A graph with asymptotes at y = x and y = −x. The first part of the graph occurs in the second and third quadrants with vertex at (−1, 0). The second part of the graph occurs in the first and fourth quadrants with vertex as (1, 0).
Asymptotes are y = x and y = x

Got questions? Get instant answers now!

x = ln ( 2 t ) , y = t 2

Got questions? Get instant answers now!

x = e −2 t , y = e 3 t

Got questions? Get instant answers now!

x = 4 sec θ , y = 3 tan θ

Got questions? Get instant answers now!

For the following exercises, convert the parametric equations of a curve into rectangular form. No sketch is necessary. State the domain of the rectangular form.

x = t 2 1 , y = t 2

x = 4 y 2 1 ; domain: x [ 1 , ) .

Got questions? Get instant answers now!

x = 1 t + 1 , y = t 1 + t , t > −1

Got questions? Get instant answers now!

x = 4 cos θ , y = 3 sin θ , t ( 0 , 2 π ]

x 2 16 + y 2 9 = 1 ; domain x [ −4 , 4 ] .

Got questions? Get instant answers now!

x = 2 t 3 , y = 6 t 7

y = 3 x + 2 ; domain: all real numbers.

Got questions? Get instant answers now!

x = 1 + cos t , y = 3 sin t

( x 1 ) 2 + ( y 3 ) 2 = 1 ; domain: x [ 0 , 2 ] .

Got questions? Get instant answers now!

x = sec t , y = tan t , π t < 3 π 2

y = x 2 1 ; domain: x [ −1 , 1 ] .

Got questions? Get instant answers now!

x = 2 cosh t , y = 4 sinh t

Got questions? Get instant answers now!

x = cos ( 2 t ) , y = sin t

y 2 = 1 x 2 ; domain: x [ 2 , ) ( , −2 ] .

Got questions? Get instant answers now!

x = 4 t + 3 , y = 16 t 2 9

Got questions? Get instant answers now!

x = t 2 , y = 2 ln t , t 1

y = ln x ; domain: x ( 0 , ) .

Got questions? Get instant answers now!

x = t 3 , y = 3 ln t , t 1

Got questions? Get instant answers now!

x = t n , y = n ln t , t 1 , where n is a natural number

y = ln x ; domain: x ( 0 , ) .

Got questions? Get instant answers now!

x = ln ( 5 t ) y = ln ( t 2 ) where 1 t e

Got questions? Get instant answers now!

x = 2 sin ( 8 t ) y = 2 cos ( 8 t )

x 2 + y 2 = 4 ; domain: x [ −2 , 2 ] .

Got questions? Get instant answers now!

x = tan t y = sec 2 t 1

Got questions? Get instant answers now!

For the following exercises, the pairs of parametric equations represent lines, parabolas, circles, ellipses, or hyperbolas. Name the type of basic curve that each pair of equations represents.

x = 3 t + 4 y = 5 t 2

line

Got questions? Get instant answers now!

x = 2 t + 1 y = t 2 3

parabola

Got questions? Get instant answers now!

x = 2 cos ( 3 t ) y = 2 sin ( 3 t )

circle

Got questions? Get instant answers now!

x = 3 cos t y = 4 sin t

ellipse

Got questions? Get instant answers now!

x = 2 cos ( 3 t ) y = 5 sin ( 3 t )

Got questions? Get instant answers now!

x = 3 cosh ( 4 t ) y = 4 sinh ( 4 t )

hyperbola

Got questions? Get instant answers now!

x = 2 cosh t y = 2 sinh t

Got questions? Get instant answers now!

Show that x = h + r cos θ y = k + r sin θ represents the equation of a circle.

Got questions? Get instant answers now!

Use the equations in the preceding problem to find a set of parametric equations for a circle whose radius is 5 and whose center is ( −2 , 3 ) .

Got questions? Get instant answers now!

For the following exercises, use a graphing utility to graph the curve represented by the parametric equations and identify the curve from its equation.

[T] x = θ + sin θ y = 1 cos θ

The equations represent a cycloid.
A graph starting at (−6, 0) increasing rapidly to a sharp point at (−3, 2) and then decreasing rapidly to the origin. The graph is symmetric about the y axis, so the graph increases rapidly to (3, 2) before decreasing rapidly to (6, 0).

Got questions? Get instant answers now!

[T] x = 2 t 2 sin t y = 2 2 cos t

Got questions? Get instant answers now!

[T] x = t 0.5 sin t y = 1 1.5 cos t


A graph starting at roughly (−6, 0) increasing to a rounded point and then decreasing to roughly (0, −0.5). The graph is symmetric about the y axis, so the graph increases to a rounded point before decreasing to roughly (6, 0).

Got questions? Get instant answers now!

An airplane traveling horizontally at 100 m/s over flat ground at an elevation of 4000 meters must drop an emergency package on a target on the ground. The trajectory of the package is given by x = 100 t , y = −4.9 t 2 + 4000 , t 0 where the origin is the point on the ground directly beneath the plane at the moment of release. How many horizontal meters before the target should the package be released in order to hit the target?

Got questions? Get instant answers now!

The trajectory of a bullet is given by x = v 0 ( cos α ) t y = v 0 ( sin α ) t 1 2 g t 2 where v 0 = 500 m/s, g = 9.8 = 9.8 m/s 2 , and α = 30 degrees . When will the bullet hit the ground? How far from the gun will the bullet hit the ground?

22,092 meters at approximately 51 seconds.

Got questions? Get instant answers now!

[T] Use technology to sketch the curve represented by x = sin ( 4 t ) , y = sin ( 3 t ) , 0 t 2 π .

Got questions? Get instant answers now!

[T] Use technology to sketch x = 2 tan ( t ) , y = 3 sec ( t ) , π < t < π .


A graph with asymptotes roughly near y = x and y = −x. The first part of the graph is in the first and second quadrants with vertex near (0, 3). The second part of the graph is in the third and fourth quadrants with vertex near (0, −3).

Got questions? Get instant answers now!

Sketch the curve known as an epitrochoid , which gives the path of a point on a circle of radius b as it rolls on the outside of a circle of radius a . The equations are

x = ( a + b ) cos t c · cos [ ( a + b ) t b ] y = ( a + b ) sin t c · sin [ ( a + b ) t b ] .
Let a = 1 , b = 2 , c = 1 .

Got questions? Get instant answers now!

[T] Use technology to sketch the spiral curve given by x = t cos ( t ) , y = t sin ( t ) from −2 π t 2 π .


A graph starting at roughly (−6, −1) decreasing to a minimum in the third quadrant near (−1, −4.8) increasing through roughly (0, −4.7) and (3, 0) to a maximum near (1, 1.9) before decreasing through (0, 1.5) to the origin. The graph is symmetric about the y axis, so the graph increases through (0, 1.5) to a maximum in the second quadrant, decreases again through (0, −4.7), and then increases to (6, −1).

Got questions? Get instant answers now!

[T] Use technology to graph the curve given by the parametric equations x = 2 cot ( t ) , y = 1 cos ( 2 t ) , π / 2 t π / 2 . This curve is known as the witch of Agnesi.

Got questions? Get instant answers now!

[T] Sketch the curve given by parametric equations x = cosh ( t ) y = sinh ( t ) , where −2 t 2 .


A vaguely parabolic graph with vertex at the origin that is open to the right.

Got questions? Get instant answers now!

Questions & Answers

What is inflation
Bright Reply
a general and ongoing rise in the level of prices in an economy
AI-Robot
What are the factors that affect demand for a commodity
Florence Reply
price
Kenu
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
Got questions? Join the online conversation and get instant answers!
Jobilize.com Reply
Practice Key Terms 7

Get Jobilize Job Search Mobile App in your pocket Now!

Get it on Google Play Download on the App Store Now




Source:  OpenStax, Calculus volume 3. OpenStax CNX. Feb 05, 2016 Download for free at http://legacy.cnx.org/content/col11966/1.2
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Calculus volume 3' conversation and receive update notifications?

Ask