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zetafunc.

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Argand Diagrams...

I know this is a bit of a stupid question, but I can't seem to think about the right way to plot a simple point on an Argand diagram, such as 2 + 3i. WolframAlpha says that this would be that point plotted on the diagram, AND a line coming from the origin to that point. However, I thought that 2 + 3i would just be a point, and that |2 + 3i| is where you draw a line to it indicating that that's the distance from O to that point.

On FP1 exam papers, I've seen them draw a line from the origin to that point most of the time. On some rare occasions I have seen them plot them as points.

So which is correct?

Bob

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Registered: 2010-06-20

Posts: 10,649

Re: Argand Diagrams...

hi zetafunc

I think you're right;  just the point (in the same way that '2' is just a point on the real number line). 

On

http://en.wikipedia.org/wiki/Argand_diagram

it says they add like vectors so there is obviously a close connection.

I'm pretty sure for FP1 it won't matter much for doing the questions.

I wonder what Argand himself said.  I'll try to find out.

EDIT:  Seems to be a common practice to define it as the set of points and then show a diagram with lines from the origin. 

And Argand didn't actually invent the idea either.  It was Caspar Wessel.

Have a happy Christmas!

Bob

Last edited by Bob (2011-12-23 11:36:53)

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