Triangle inequality for complex numers

In summary, the conversation was about solving the inequality |(|z|-|z'|)|<=|z-z'| using complex numbers. The person initially had the reverse inequality and was trying to figure out where they went wrong. The other person asked for a detailed explanation of the algebraic steps taken and suggested visualizing the numbers as vectors on an argand diagram. Eventually, the person found their mistake of multiplying by a negative number and not accounting for the sign change.
  • #1
pivoxa15
2,255
1

Homework Statement


show
|(|z|-|z'|)|<=|z-z'|




The Attempt at a Solution



I used z=a+ib and z'=a'+ib' and ended up with the reverse inequality to the above by proving (ab'-ba')^2>=0 hence the reverse of the sign above. Where have I gone wrong?
 
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  • #2
Well, I don't know what you did wrong if I can't see what you did!
 
  • #3
Good point. Bascially I expanded the complex numbers out and squared them.
 
  • #4
Ok, you're not getting the point here. Show me exactly what you did, in algebra, and I can see whether you are correct or not.
 
  • #5
Think of the numbers like vectors and draw them on an argand diagram...you'll get a triangle...and two sides added should be greater than the third side...so...vice versa
 
  • #6
I found my mistake. I multiplied by a negative number along the way so the sign was flipped and I didn't account for that when I first did it.
 

FAQ: Triangle inequality for complex numers

1. What is the Triangle Inequality for complex numbers?

The Triangle Inequality for complex numbers states that the absolute value of the sum of two complex numbers is less than or equal to the sum of the absolute values of the two complex numbers. In other words, the length of the third side of a triangle formed by two complex numbers is always shorter than the sum of the lengths of the other two sides.

2. Why is the Triangle Inequality important?

The Triangle Inequality is important because it helps us understand the relationship between the lengths of the sides of a triangle formed by complex numbers. It also helps us solve problems involving complex numbers and their magnitudes.

3. How is the Triangle Inequality related to the Pythagorean Theorem?

The Pythagorean Theorem is a special case of the Triangle Inequality when dealing with real numbers. It states that in a right triangle, the square of the length of the hypotenuse is equal to the sum of the squares of the other two sides. This can be seen as a special case of the Triangle Inequality because in a right triangle, the length of the hypotenuse is always longer than the sum of the lengths of the other two sides.

4. Can the Triangle Inequality be extended to more than two complex numbers?

Yes, the Triangle Inequality can be extended to any number of complex numbers. It states that the absolute value of the sum of any number of complex numbers is less than or equal to the sum of the absolute values of the individual complex numbers.

5. How can the Triangle Inequality be used in real-life applications?

The Triangle Inequality has many real-life applications in fields such as engineering, physics, and signal processing. It can be used to analyze and optimize networks, design efficient communication systems, and solve problems involving complex numbers in various fields of science and technology.

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