### Re: how to calculate parameter?

Ari Diacou
Fri, Jan 7, 2022 5:27 PM

The points on the yellow tile should be on the corners of a square, so I
think you need ot replace 1.4 with sqrt(2), which is ~1.41.

On Fri, Jan 7, 2022 at 12:14 PM fred via Discuss discuss@lists.openscad.org
wrote:

---------- Forwarded message ----------
From: fred fred_dot_u@yahoo.com
Cc:
Bcc:
Date: Fri, 7 Jan 2022 17:08:44 +0000 (UTC)
Subject: [OpenSCAD] how to calculate parameter?
\$fn = 60;
dia = 15;
t_factor = 1.4;
circle(dia);
translate([t_factor * dia, 0, 0])
color("blue")
circle(dia);
translate([-t_factor * dia, 0, 0])
color("green")
circle(dia);

[image: Inline image]

I've not performed any tests on the current t_factor (translate factor) as
it's more-or-less a rough eyeball guess. I've forgotten most of my high
school trigonometry/geometry (last century) and am not certain that what I
knew would help me here.

I'd like to know what formula to use to calculate the x-translation that
results in the green and blue circles to split the yellow circle's
circumference into quarters. The final objective is to create a shape which
when duplicated and rotated will be tiled without gaps.

[image: Inline image]
This is the shape which results from using sqrt(2) as the translation
factor. I expect that this is the correct answer, but I only stumbled on
it. It's been my experience that sometimes a calculation falls into one of
the "standard" references in the world.

Can someone explain the development that would confirm this as the correct
calculation?

---------- Forwarded message ----------