Complex Numbers VI: Finding Least Value of |z-2√2-4i|

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Discussion Overview

The discussion revolves around finding the least value of the expression |z-2√2-4i|, given certain constraints on the complex number z. The context includes sketching loci on an Argand diagram and determining the intersection of these loci to identify the point that minimizes the expression.

Discussion Character

  • Exploratory
  • Mathematical reasoning
  • Homework-related

Main Points Raised

  • One participant sketches the loci defined by |z-4i|≤√5 and the argument constraints, indicating a need to find the least value of |z-2√2-4i|.
  • Another participant questions the set of z over which the least value is to be found, suggesting it involves the intersection of the defined loci and the shortest distance from a point to a semi-disk.
  • There is a request for clarification on how to find the complex number z_1 that minimizes the expression, with a mention of difficulties using LaTeX for mathematical notation.
  • Participants express confusion about the proper formatting of mathematical expressions in their posts.

Areas of Agreement / Disagreement

Participants generally agree on the need to find the least value of the expression and the relevance of the intersection of loci, but there is uncertainty regarding the specific method to determine z_1 and the formatting of mathematical expressions.

Contextual Notes

There are unresolved issues regarding the application of LaTeX for mathematical expressions and the exact nature of the intersection of the loci, which may affect the clarity of the discussion.

Punch
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Sketch on an Argand diagram the set of points satisfying both |z-4i|<=\sqrt{5} and \frac{\pi}{4}<=arg(z+4)<=\frac{\pi}{2}.

I have already sketched the 2 loci. The problem lies in the following part.

Hence find the least value of |z-2\sqrt{2}-4i|. Find, in exact form, the complex number z_1 represented by the point P that gives this least value.
 
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Punch said:
Hence find the least value of |z-2\sqrt{2}-4i|.
Over which set of z? The intersection defined in the first part? It seems that you need to find the shortest distance from a point to a semi-disk.

Why don't you wrap the [tex]...[/tex] tags around your formulas?
 
Evgeny.Makarov said:
Over which set of z? The intersection defined in the first part? It seems that you need to find the shortest distance from a point to a semi-disk.

Why don't you wrap the \(z_1\) tags around your formulas?

Yes, how do I then find the complex number z_1 in the following part?

I tried using the latex but they didnt seem to work
 
Punch said:
Yes, how do I then find the complex number z_1 in the following part?
See the following picture.

argand.png


Punch said:
I tried using the latex but they didnt seem to work
Type [tex]\frac{\pi}{4}\le\arg(z+4)\le\frac{\pi}{2}[/tex] to get \frac{\pi}{4}\le\arg(z+4)\le\frac{\pi}{2}.
 

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