Lagrange multipliers and triangles

In summary, Lagrange Multipliers can be used to find the maximum area of an equilateral triangle with a given perimeter by constructing a constraint function for the area and applying the theory. This method allows for important information, such as the length of the sides, to be found without explicitly solving for them.
  • #1
physicsss
319
0
Use Lagrange Multipliers to prove that the triangle with the maximum area that has a given perimeter p is equilateral.
[Hint: Use Heron’s formula for the area of a triangle: A = sqrt[s(s - x)(s - y)(s - z)] where s = p/2 and x, y, and z are the lengths of the sides.]

I have no idea how to do this.
 
Physics news on Phys.org
  • #2
U have a function of 3 varibles (the area) and a constraint depending on these 3 variables (the perimeter is constant).So basically construct the constaint "area" function and then apply the theory...

Daniel.
 
  • #3
Are you saying that you don't know what "Lagrange multipliers" are?

The problem is to maximize [tex]A= \sqrt{s(s-x)(s-y)(s-z)}[/tex] subject to the condition x+ y+ z= p.

One nice thing about "Lagrange multipliers" is that we can find important information
(like x= y= z) without having to find x, y, z specifically- eliminate the "multiplier" [tex] \lambda [/tex] from the equations and see what happens.
 
Last edited by a moderator:

1) What are Lagrange multipliers and how are they used in triangles?

Lagrange multipliers are a mathematical tool used to find the maximum or minimum value of a function subject to constraints. In terms of triangles, they are used to find the maximum or minimum value of a function (such as area or perimeter) while also satisfying the constraints of the triangle (such as fixed side lengths or fixed angles).

2) How do you set up a Lagrange multiplier problem for triangles?

To set up a Lagrange multiplier problem for triangles, you first need to define the function you want to optimize (e.g. area or perimeter) and the constraints of the triangle (e.g. fixed side lengths or fixed angles). Then, you create a Lagrangian function by adding the product of the function and a Lagrange multiplier to the constraints. Finally, you take the partial derivatives of the Lagrangian function with respect to the variables and set them equal to zero to solve for the optimal values.

3) Can Lagrange multipliers be used for any type of triangle?

Yes, Lagrange multipliers can be used for any type of triangle as long as the constraints are well-defined and the function being optimized is continuous. This includes equilateral, scalene, and right triangles.

4) What are some real-world applications of Lagrange multipliers in triangles?

Lagrange multipliers in triangles have various real-world applications, such as optimizing the use of material in construction projects, finding the most efficient shapes for objects like airplane wings, and maximizing the area of a bounded region for landscaping purposes.

5) Are there any limitations to using Lagrange multipliers in triangles?

One limitation of using Lagrange multipliers in triangles is that they can only be used for optimization problems with continuous functions. Additionally, they may not always provide the global maximum or minimum value, and multiple solutions may exist. In these cases, further analysis or numerical methods may be needed to find the optimal solution.

Similar threads

I The Euler-Lagrange equation and the Beltrami identity
    • Calculus
Replies
1
Views
935
MHB Optimization - Lagrange multipliers : minimum cost/maximum production
    • Calculus
Replies
3
Views
1K
How should I find the nontrivial stationary paths?
    • Calculus and Beyond Homework Help
Replies
10
Views
362
MHB Solve Lagrange Multipliers Problem w/ e^(9x) - Find (a,b)
    • Calculus
Replies
2
Views
938
Lagrange multipliers understanding
    • Calculus and Beyond Homework Help
Replies
8
Views
468
B Why do I not understand what seems to be basic Calculus?
    • Calculus
Replies
11
Views
2K
Find Relative Extrema of f|s: Explained with Lagrange Multipliers
    • Calculus
Replies
7
Views
2K
MHB Solving Lagrange Multipliers: Find Extrema of Distance from (1,2,3) to Sphere
    • Calculus
Replies
7
Views
2K
1st year high school geometry proof
    • Precalculus Mathematics Homework Help
Replies
14
Views
556
I Lipschitz continuity of vector-valued function
    • Calculus
Replies
3
Views
1K

Hot Threads

Recent Insights

Back
Top