Mathematica Mathematica question - plotting an equation

[kidsmoker]

How could I use Mathematica to give me a plot of the locus of z such that

\arg(\frac{z-2}{z+5}) = \frac{\pi}{4} ?

I've tried using ContourPlot and typing

ContourPlot[Arg[(x - 2 + I)/((x + 5) + I)] == (\[Pi]/4), {x, -5, 5}, {y, -5, 5}]

but it just gives me two vertical lines. I think the correct graph should be the arc of a circle passing through (-5,0) and (2,0).

Many thanks!

 

[alphysicist]

Hi kidsmoker,

How could I use Mathematica to give me a plot of the locus of z such that

\arg(\frac{z-2}{z+5}) = \frac{\pi}{4} ?

I've tried using ContourPlot and typing

ContourPlot[Arg[(x - 2 + I)/((x + 5) + I)] == (\[Pi]/4), {x, -5, 5}, {y, -5, 5}]

but it just gives me two vertical lines. I think the correct graph should be the arc of a circle passing through (-5,0) and (2,0).

Many thanks!

I think the reason it is giving vertical lines is because you have left out the y variable in your Arg function. I believe it should be:

Arg[(x - 2 + y I)/((x + 5) + y I)]

Does that work?

 

[kidsmoker]

Got it! Thanks very much :-)