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Regular Member

Plotting circle

Hi everyone.

I'm trying to plot 2 lines and a circle in mathcad prime 4, in the form (x-x0)^2+(y-y0)^2=R^2.

I have values for x0 and y0 and R, but I can't figure out how to plot it. Solving for y gives me complex numbers.

x0 and y0 are defined values of some earlier calculations, so their value can change, so they are not "fixed" numbers.

Any simple way to do this? (Seems all the info on this I can find is pretty old, and I can't open example files and such...)

5 REPLIES 5

Re: Plotting circle

One way is as follows:

i:=0..360

thetai = i*deg    (i as a subscript on theta)

x:=x0+R*cos(theta)

y:=y0+R*sin(theta)

Then simply plot y vs x.

Alan

Re: Plotting circle

Ok, that works. Thanks.

- Any way to make it a function of x? That would be great, that way I could check intersection points with the lines..

Re: Plotting circle

You can plot versus x, but it's a double-valued function:

Re: Plotting circle

You may use your appraoch even though the symbolic result uses the imaginary unit (the values derived are real anyway):

To get a closed curve you may define a range variable for plotting as Fred had shown.

But a better approach IMHO is to use different representations for calculations and for plotting. The parameter representation Alan suggested is best suited for plotting. I prefer a small program which returns a matrix of x and y-values of the points of any circle which can be used easily to plot different circles:

You may use this in the following way. I also plotted the two lines which as it looks are nearly tangents of the circle:

Worksheet in format P5 attached

Re: Plotting circle

n=100

Using posted techniques.