Author Topic: Isocircles  (Read 183 times)

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notredave

  • Newt
  • Posts: 133
Isocircles
« on: August 05, 2020, 10:52:53 AM »
Good morning,

I am having a time trying to get an ellipse-->isocircle in isodraft to give me the correct diameter when I do a distance between quadrants. For example, if I draw an isocircle with a diameter of 1" and dimension it, it gives 1.2247" across quadrants. Is there a way to draw an isocircle with diameter inputted to output correct diameter when dimensioning it?

Thank you,
Dave

Crank

  • Swamp Rat
  • Posts: 1466
Re: Isocircles
« Reply #1 on: August 05, 2020, 03:35:39 PM »
It's just math (in radians)
If you draw a circle with radius=1 and add some lines and angles, we get:
Code: [Select]
(setq Rmin (cos (* pi .25)))
(setq Rmax (* Rmin (sqrt 3.)))
So:
Code: [Select]
(setq Rmin (* 0.5 (sqrt 2.)))
(setq Rmax (* 0.5 (sqrt 6.)))
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