Drawing Tangent Lines

[Anonymous]

I've hit upon an annoying defficiency in ArchiCAD, again, and I'm wondering if anybody out there has a solution (aka: workaround).

How do you draw a line that's tangent to two circles? I have a site plan with property lines at some odd angles which are not dimensioned. All I have to go on is some dimensions that locate the corner of the building. Going the reverse route, I need to ... [long story short] ... draw a line that's tangent to 2 circles.

I've tried two different ways of constructing the tangent line geometrically, but the solution always ends up being "slighly" off (depending on the scale. For a site plan you're talking feet - a considerable problem).

So does anybody have any suggestions?

Thanks in advance.

[Anonymous]

Here it is

[Djordje]

Sergio wrote:
How do you draw a line that's tangent to two circles?

http://archicad-talk.graphisoft.com/viewtopic.php?t=485

http://archicad-talk.graphisoft.com/viewtopic.php?p=2456#2456

HTH,

[Steve Jepson]

Djordj,

I don't think the illustrations you posted work.

The line the illustration makes is only part of the process.
The line proposed will create chords across two circles. (sometimes very small) However, it is the perpendicular bisector of these chords the will locate the true points tangent.