Lagrange multipliers and triangles

Click For Summary
SUMMARY

The discussion focuses on using Lagrange multipliers to demonstrate that the triangle with the maximum area for a fixed perimeter \( p \) is equilateral. The area \( A \) is defined using Heron’s formula: \( A = \sqrt{s(s - x)(s - y)(s - z)} \), where \( s = \frac{p}{2} \). Participants emphasize the importance of setting up the constraint \( x + y + z = p \) and applying Lagrange multipliers to derive the condition \( x = y = z \) without explicitly solving for the side lengths.

PREREQUISITES
  • Understanding of Lagrange multipliers
  • Familiarity with Heron’s formula for triangle area
  • Basic knowledge of calculus and optimization techniques
  • Ability to manipulate algebraic expressions and constraints
NEXT STEPS
  • Study the application of Lagrange multipliers in optimization problems
  • Explore Heron’s formula in depth for various triangle configurations
  • Learn about geometric interpretations of optimization constraints
  • Investigate other methods for maximizing area under constraints, such as the method of substitution
USEFUL FOR

Mathematicians, engineering students, and anyone interested in optimization techniques in geometry will benefit from this discussion.

physicsss
Messages
319
Reaction score
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
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.
 
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:

Similar threads

  • · Replies 7 ·
Replies
7
Views
2K
Replies
7
Views
2K
  • · Replies 1 ·
Replies
1
Views
10K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 8 ·
Replies
8
Views
3K
Replies
9
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 6 ·
Replies
6
Views
7K
  • · Replies 3 ·
Replies
3
Views
3K