Prove Triangle Inequality for Complex Numbers z1 and z2

In this case, we can apply the triangle inequality to the right hand side, which becomes |z2-z1| \leq |z2|+|z1|. Then, by subtracting |z1| from both sides, we get |z2|-|z1|\leq |z2-z1|. This proves that the left hand side is less than or equal to the right hand side, as required. In summary, we can prove that |z2|-|z1| \leq |z2-z1| using the triangle inequality.
  • #1
stunner5000pt
1,461
2
Edit: Nevermind i got it, thanks anyway

for complex numbers z1 and z2

prove that [tex] |z_{2}| - |z_{1}| \leq |z_{2} - z_{1}| [/tex]
the left hand side becomes
[tex] \sqrt{x_{2}^2 + y_{2}^2} - \sqrt{x_{1}^2 + y_{1}^2} [/tex]

the right hand side becomes
[tex] \sqrt{(x_{2} - x_{1})^2 + (y_{2} - y_{1})^2} [/tex]

now i tried squaring both sides and i get
left hand side
[tex] x_{2}^2 + y_{2}^2 + x_{1}^2 + y_{1}^2 - 2 \sqrt{(x_{2}x_{1})^2 + (x_{2}y_{1})^2 + (x_{1}y_{2})^2 + (y_{1}y_{2})^2} [/tex]

right hand side
[tex] (x_{2} - x_{1})^2 + (y_{2} - y_{1})^2 [/tex]
i put the two of them not equal to eah other and reduce and i ended up with
[tex] x_{2}^2 y_{1}^2 + x_{1}^2 y_{2}^2 \neq 2x_{1} x_{2} y_{1} y_{2} [/tex]
im stuck now...

please help
is there a simpler... less tedious way of doing this... by the way?
 
Last edited:
Physics news on Phys.org
  • #2
The less tedious way is to use the triangle inequality: [itex]|z-w|\leq |z|+|w|[/itex]
 

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 individual complex numbers. In mathematical notation, this can be written as |z1 + z2| ≤ |z1| + |z2|.

2. Why is the Triangle Inequality important?

The Triangle Inequality is important because it allows us to determine the maximum possible length of a side in a triangle formed by three complex numbers. It also helps us understand the relationship between the magnitudes of complex numbers and their sums.

3. How is the Triangle Inequality proved for complex numbers?

The Triangle Inequality can be proved using the properties of complex numbers and the properties of absolute values. We can start by expressing z1 and z2 in terms of their real and imaginary parts, and then use the properties of absolute values to simplify the expression. Finally, we can use the properties of complex conjugates to show that the absolute value of z1 + z2 is less than or equal to the sum of the absolute values of z1 and z2.

4. Are there any other inequalities for complex numbers?

Yes, there are other inequalities for complex numbers, such as the Cauchy-Schwarz Inequality and the Triangle Inequality for vectors. These inequalities are useful in various mathematical applications, such as geometry, number theory, and physics.

5. 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. For example, if we have three complex numbers z1, z2, and z3, the Triangle Inequality states that |z1 + z2 + z3| ≤ |z1| + |z2| + |z3|. This can be generalized to n complex numbers as well.

Similar threads

  • Introductory Physics Homework Help
Replies
1
Views
195
  • Quantum Physics
Replies
19
Views
2K
Replies
1
Views
571
  • Calculus and Beyond Homework Help
Replies
12
Views
1K
Replies
18
Views
2K
  • Calculus and Beyond Homework Help
Replies
4
Views
1K
  • Calculus and Beyond Homework Help
Replies
10
Views
3K
  • Calculus and Beyond Homework Help
Replies
8
Views
1K
  • Calculus and Beyond Homework Help
Replies
2
Views
1K
  • Calculus and Beyond Homework Help
Replies
1
Views
2K
Back
Top