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VCE Stuff => VCE Mathematics => VCE Mathematics/Science/Technology => VCE Subjects + Help => VCE Specialist Mathematics => Topic started by: /0 on March 31, 2009, 06:47:11 pm

Title: Argand Diagram
Post by: /0 on March 31, 2009, 06:47:11 pm: When graphing on the argand diagram, do you write points in the form $1+2i$ , $(1,2i)$ , or $(1,2)$ ?
My teacher reckons you can write it like (1,2), but what about when describing loci?

e.g. Describe the locus of $|z-(1+i)|=1$ .

$\Rightarrow (x-1)^2+(y-1)^2=1$ .

$\therefore$ Circle centre (1,1) radius 1.

Would this technically be incorrect, since the locus description does not explicitly refer to an Argand Diagram? (The locus might as well describe a circle on the x-y plane)

Also, when drawing other things on the argand diagram, like straight lines, would you say $x+y=1$ or $Re(z)+Im(z)=1$ ?
Title: Re: Argand Diagram
Post by: TrueTears on March 31, 2009, 06:54:56 pm: yeah... i asked him the same thing, he said you can just write it as (1,2)
Title: Re: Argand Diagram
Post by: dejan91 on March 31, 2009, 06:58:09 pm: I use (1,2). I guess it's fine as long as you have the Re(z) and Im(z) axis marked.
Title: Re: Argand Diagram
Post by: /0 on March 31, 2009, 07:41:18 pm: Yeah thanks guys, but when you describe the locus do you have to say it is on the Argand diagram or could you lose marks if you don't?
Title: Re: Argand Diagram
Post by: TrueTears on March 31, 2009, 07:43:08 pm: Describe the locus just means describe it lol eg

$(x-1)^2+(y-1)^2=1.$

all you have to say is circle centre at (1,1) radius 1.
Title: Re: Argand Diagram
Post by: /0 on March 31, 2009, 07:54:17 pm: Quote from: TrueTears on March 31, 2009, 07:43:08 pm
Describe the locus just means describe it lol eg

$(x-1)^2+(y-1)^2=1.$

all you have to say is circle centre at (1,1) radius 1.

Ok thanks, I'll just leave it like that then... just saying, there is a difference isn't there?
Title: Re: Argand Diagram
Post by: TrueTears on March 31, 2009, 07:55:42 pm: nope, i remember specifically there was a question in the essentials book that said 'describe' the locus. The answer just stated what i did just then

In fact if that was w = 2z question. Have a check if you wish :)