When does the triangle inequality hold for absolute value?

Click For Summary

Homework Help Overview

The discussion revolves around the triangle inequality in the context of absolute values, specifically examining the condition under which the equality abs(x+y+z) = abs(x) + abs(y) + abs(z) holds. Participants are tasked with exploring this mathematical concept and proving the statement.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss the absolute value function and consider various cases based on the signs of the variables involved. There is mention of creating a case analysis to explore the conditions for equality, as well as a desire for a more elegant solution.

Discussion Status

The discussion is ongoing, with participants sharing different perspectives on how to approach the problem. Some have suggested case analysis, while others are questioning the necessity of such an approach. There is no explicit consensus on the method to be used.

Contextual Notes

Participants are working under the constraints of a homework assignment, which may influence their approaches and the level of detail they provide in their reasoning.

lepton123
Messages
11
Reaction score
0

Homework Statement


abs(x+y+z)≤abs(x)+abs(y)+abs(z) indicate when this equality holds and prove this statement


Homework Equations



Triangle inequality?

The Attempt at a Solution


I have nothing :/
 
Physics news on Phys.org
What is the absolute value of x? if x => 0 then abs(x)=x, else it is -x.

So make a table with all of the possible cases and see what happens!
 
Drat, I was hoping that that I wouldn't have to do a case analysis; is there a more elegant way of solving this though?
 
I don't know elegant ... I grew up on a farm!

So once you have carried out the detailed work you can apply your own standards of elegance and cleverness ... and write something elegant!
 
Assume (by renaming of variables) that x ≤ y ≤ z. Then you have 4 cases to check, it shouldn't be too tedious.
 
x + y + z <= |x| + |y| + |z|
- x - y - z <= |x| + |y| + |z|

(definition of the absolute value)
 

Similar threads

  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 9 ·
Replies
9
Views
3K
  • · Replies 9 ·
Replies
9
Views
2K
  • · Replies 6 ·
Replies
6
Views
2K
Replies
9
Views
2K
  • · Replies 5 ·
Replies
5
Views
2K
  • · Replies 5 ·
Replies
5
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K