calculate the correct space between dots on a dashed circle, to have a perfect alignment I want to draw a dashed circle, with a diameter D, and X dots composing the circle, like on this image:
dashed circle
How can I define the exact space I should have between the different dots, to avoid the misalignment you can see on the right of the circle?
I think that an equation involving D, X, and Pi should work, but I do not find the solution...
Many thanks!

If you want $X$ dots the angle between two  successive dots is $\alpha=2\pi/X$ and the distance between them, measured as an arc on the circle, is $D \alpha/2$.
All this come form the fact that $c=2 \pi r$.
