Mail Archives: djgpp/1997/02/02/22:12:00
On Sun, 2 Feb 1997, Gurunandan R Bhat wrote:
> > On 1 Feb 1997 20:32:31 GMT hotpulp AT netidea DOT com writes:
>
> > >I was wondering: how would I go about drawing an ellipse that has its
> > >major and minor axis at an angle? If you're having trouble
>
>
>
> its not very different from drawing a circle. for an ellipse, you do:
>
> x = r1 * cos(t); y = r2 * sin (t)
>
> if r1 is the same as r2 you get a circle. if you want a shifted ellipse,
> by an angle a say, do this:
>
> x = r1 * cos(t + a) ; y = r2 * sin(t + a)
>
> for a whole set of values of t from 0 to 360.
sorry the last point was a mistake.
the correct formula to turn an ellipse through angle a should read
x = r1 * cos(t) * cos(a) + r2 * sin(t) * sin(a)
y = -r1 * cos(t) * sin(a) + r2 * sin(t) * cos(a)
apologies for the slip.
gurunandan
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