Is it possible to reduce this inequality to (|x| - |y|)² ≥ 0?

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In summary, to prove that the inequality Square root (2) * lzl >= l Re (z) l + l I am ( z ) l is true, we can start with the expression 2(x² + y²) ≥ (|x| + |y|)² and use the fact that 2(x² + y²) = |x|² + |x|² + |y|² + |y|² to simplify our approach.
  • #1
selena
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One Question...Complex Numbers

Homework Statement



verify that: Square root (2) * lzl >= l Re (z) l + l I am ( z ) l


suggestion : reduce this inequality to ( lxl - lyl )^2 >=0

note : lxl <<<< modulus x
 
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  • #2


Well, what have you TRIED? If z= x+ iy, what is |z|? Whar are Re(z) and Im(z)?

I assume your note simply means that |x| and "modulus x" are the same thing. I had first interpreted it as "much less than" which makes no sense!
 
  • #3


lxl <<<< modulus x<<<< i dosent mean less thab but i mean modulus x ---->lxl
i mean modulus x = lxl

((2x2+2y2)1/2 - lxl - lyl )2 >= 0

Substitute lxl - lyl = k
2x2 + 2y2 - 2k * (2x2 + 2y2)1/2 + k2 >= 0

Substitute 2x2 + 2y2 = m

m - 2k * m1/2 + k2 >= 0

this is my try ...
i know its wrong ...
and i can't continue ...
 
Last edited:
  • #4


You're going the wrong way. From your attempt it looks like you know |z|=sqrt(x^2+y^2) for z=x+iy. Start with what you want to prove. sqrt(2)*sqrt(x^2+y^2)>=|x|+|y|. Square both sides. Now move everything to one side and look at your suggestion.
 
  • #5
Welcome to PF!

Hi selena! Welcome to PF! :smile:

(have a square root: √ and a square: ² :wink:)

Do you mean 2(x² + y²) ≥ (|x| + |y|)²?

hmm … let's keep it simple … :rolleyes:

Hint: 2(x² + y²) = |x|² + |x|² + |y|² + |y|² :smile:
 

FAQ: Is it possible to reduce this inequality to (|x| - |y|)² ≥ 0?

1. What are complex numbers and how are they different from real numbers?

Complex numbers are numbers that have a real part and an imaginary part. They are typically written in the form a + bi, where a is the real part and bi is the imaginary part. Real numbers only have a single value on the number line, while complex numbers have a two-dimensional representation on the complex plane.

2. How do you add, subtract, multiply, and divide complex numbers?

To add or subtract complex numbers, simply combine the real parts and the imaginary parts separately. To multiply complex numbers, use the FOIL method just as you would with binomials. To divide complex numbers, multiply the numerator and denominator by the complex conjugate of the denominator, which is the same expression with the sign of the imaginary part flipped.

3. What is the significance of the imaginary unit, i, in complex numbers?

The imaginary unit, i, is defined as the square root of -1. It allows us to represent numbers that cannot be represented on the real number line. It also plays a crucial role in the fundamental theorem of algebra and in many other mathematical applications.

4. How are complex numbers used in real life?

Complex numbers have various applications in fields such as engineering, physics, and economics. They are used to describe oscillatory motion, electrical circuits, and control systems. They are also used in signal processing and image processing.

5. Can complex numbers have real world values?

Yes, complex numbers can have real world values. For example, in electrical engineering, the impedance of a circuit can be a complex number with both a real and imaginary component. In physics, the wave function in quantum mechanics can also be represented by a complex number. Complex numbers are often used to model and solve real world problems.

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