All Calculus 3 Resources
Example Questions
Example Question #14 : Applications Of Partial Derivatives
Find the maximum value of the function with the constraint .
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To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
The equation being optimized is .
The constraint is .
, , ,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Setting the two expressions for equal to each other gives us
Substituting this expression into the constraint gives us
Example Question #2 : Lagrange Multipliers
Find the maximum value of the function with the constraint .
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,
,
,
,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
The equation being optimized is .
The constraint is .
, , ,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Setting the two expressions for equal to each other gives us
Substituting this expression into the constraint gives us
Example Question #16 : Applications Of Partial Derivatives
A company makes chairs () and benches (). The profit equation for this company is . The company can only produce pieces per day. How many of each seat should the company produce to maximize profit?
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To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
In this problem, we are trying to maximize the profit, so the equation being optimized is .
The company can only produce pieces of furniture, so the constraint is .
,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Setting the two expressions of equal to each other gives us
Substituting this expression into the constraint gives
Profit is maximized by making chairs and benches.
Example Question #17 : Applications Of Partial Derivatives
A company makes end tables () and side tables (). The profit equation for this company is . The company can only produce pieces per day. How many of each table should the company produce to maximize profit?
,
,
,
,
,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
In this problem, we are trying to maximize the profit, so the equation being optimized is .
The company can only produce pieces of furniture, so the constraint is .
,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Setting the two expressions of equal to each other gives us
Substituting this expression into the constraint gives
Profit is maximized by making end tables and side tables.
Example Question #18 : Applications Of Partial Derivatives
Production is modeled by the function, where is the units of labor and is the units of capital. Each unit of labor costs and each unit of capital costs . If a company has to spend, how many units of labor and capital should be purchased.
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,
,
,
,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
In this problem, we are trying to maximize the production, so the equation being optimized is .
We have a finite amount of money to purchase labor and capital, so the constraint is .
,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Solving the first two equations for lambda gives
Setting the two expressions of equal to each other gives us
Substituting this expression into the constraint gives
Buying units of labor and units of capital will maximize production.
Example Question #11 : Applications Of Partial Derivatives
Production is modeled by the function where is the units of labor and is the units of capital. Each unit of labor costs and each unit of capital costs . If a company has to spend, how many units of labor and capital should be purchased.
,
,
,
,
,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
In this problem, we are trying to maximize the production, so the equation being optimized is .
We have a finite amount of money to purchase labor and capital, so the constraint is .
,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Solving the first two equations for lambda gives
Substituting this expression into the constraint gives
Buying units of labor and units of capital will maximize production.
Example Question #20 : Applications Of Partial Derivatives
A tiger cage is being built at the zoo (it has no bottom). Its surface area is . What dimensions maximize the surface area of the box?
, ,
, ,
, ,
, ,
, ,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a three-dimensional function, the Lagrangian function expands to three equations,
, and .
In this problem, we are trying to maximize the volume of the cage, so the equation being optimized is .
The constraint is the surface area of the box with no bottom, or .
, , ,
, ,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have four equations and four variables (,, and ), so we can solve the system of equations.
Multiplying the first equation by and the second equation by gives us
The left side of both equations are the same, so we can set the right sides equal to each other
Multiplying the first equation by and the second equation by gives us
The left side of both equations are the same, so we can set the right sides equal to each other
Substituting and into the constraint gives us
These dimensions maximize the volume of the box.
Example Question #11 : Lagrange Multipliers
A box has a surface area of . What length, width and height maximize the volume of the box?
, ,
, ,
, ,
, ,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a three-dimensional function, the Lagrangian function expands to three equations,
, and .
In this problem, we are trying to maximize the volume of the box, so the equation being optimized is .
The constraint is the surface area of the box, or .
, , ,
, ,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have four equations and four variables (,, and ), so we can solve the system of equations.
Multiplying the first equation by and the second equation by gives us
The left side of both equations are the same, so we can set the right sides equal to each other
Multiplying the first equation by and the second equation by gives us
The left side of both equations are the same, so we can set the right sides equal to each other
We now know . Substituting and into the constraint gives us
These dimensions maximize the volume of the box.
Example Question #11 : Lagrange Multipliers
A fish tank (right cylinder) with no top has a volume of . What height and radius will minimize the surface area of the fish tank?
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,
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To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
In this problem, we are trying to minimize the surface area of the fish tank with no top, so the equation being optimized is .
The constraint is the volume of the cylinder, or .
, , ,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Setting both expressions of lambda equal to each other gives us
Substituting this expression into the constraint, we have
These dimensions minimize the surface area of the fish tank.
Example Question #13 : Lagrange Multipliers
A soda can (a right cylinder) has a volume of . What height and radius will minimize the surface area of the soda can?
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,
,
,
,
To optimize a function subject to the constraint , we use the Lagrangian function, , where is the Lagrangian multiplier.
If is a two-dimensional function, the Lagrangian function expands to two equations,
and .
In this problem, we are trying to minimize the surface area of the soda can, so the equation being optimized is .
The constraint is the volume of the cylinder, or .
, , ,
Substituting these variables into the the Lagrangian function and the constraint equation gives us the following equations
We have three equations and three variables (,, and ), so we can solve the system of equations.
Setting both expressions of lambda equal to each other gives us
Substituting this expression into the constraint, we have
These dimensions minimize the surface area of the soda can.
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