Proving the Triangle Inequality in Real Analysis: abs(abs(x)-abs(y))<=abs(x-y)

In summary, a proof in real analysis is a logical argument that demonstrates the validity of a mathematical statement or theorem in the context of real numbers. It is considered complete when all the steps are clearly and logically presented and rigor is crucial in ensuring the validity of the conclusion. Some common techniques used in proofs include induction, contradiction, and epsilon-delta arguments, and there is no set structure but it typically follows a logical flow and includes all necessary information and examples.
  • #1
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Homework Statement



Prove: abs(abs(x)-abs(y))<=abs(x-y)

Homework Equations



Triangle Inequality:
abs(a+b)<=abs(a)+abs(b)

The Attempt at a Solution



This is what i have so far:

Let a=x-y and b=y. Then
abs(x-y+y) <= abs(x-y)+abs(y) which becomes abs(x)-abs(y)<=abs(x-y). From here i get stuck can anybody help me?
 
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  • #2
Well you've got half of it. The other inequality you need to demonstrate is |y| - |x| <= |x-y|. But what is an equivalent way of writing |x-y|?
 

1. What is the definition of a proof in real analysis?

A proof in real analysis is a logical argument that demonstrates the validity of a mathematical statement or theorem in the context of real numbers. It typically involves using axioms, definitions, and previously proven theorems to arrive at a conclusion.

2. How do you know when a proof in real analysis is complete?

A proof in real analysis is considered complete when all the steps are clearly and logically presented, and there are no gaps or errors in the reasoning. It should also be able to withstand scrutiny and convince other mathematicians of its validity.

3. What are some common techniques used in proofs in real analysis?

Some common techniques used in proofs in real analysis include induction, contradiction, and the use of epsilon-delta arguments. Other techniques may include using inequalities, limits, and continuity properties of real numbers.

4. How important is rigor in a proof in real analysis?

Rigor is crucial in a proof in real analysis as it ensures that the argument is logically sound and that the conclusion is mathematically valid. A lack of rigor can lead to incorrect or invalid results, which can be detrimental to the overall understanding of a mathematical concept.

5. Is there a specific way to structure a proof in real analysis?

There is no set structure for a proof in real analysis, but it typically follows a logical flow from the given information to the conclusion. It is important to clearly state all assumptions, definitions, and previously proven theorems used in the proof. Additionally, it is common to include diagrams or examples to aid in understanding.

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