Line tangent to arc or circle in draft mode

[jfc4120]

Can someone please do a macro that does that?

[Workshop_Notes]

Are you aware of the geometric construction that can do this? That might be a work around for you. Clearly, if you need it a hundred times, it will be very slow, but once or twice, it is not so bad.

This is how to draw a line tangent to a circle from a point in space. Note that the point has to be outside the circle. Draw a line from the point to the centre of the circle. At the midpoint of that line, draw a circle with diameter the length of the line. Where that circle intersects the original circle is the point of tangency.

I have Python code for this, which takes the external point, the centre and radius of the circle and a selected point* as inputs and outputs the tangent point but I do not know how to make it interact with FC. I think it would be fairly easy to modify this for a tangent from a point to an ellipse. Also, if it is of interest, I have code to draw the common tangent between two circles.

* because there are generally two possible tangents to a circle from any external point. The selected point determines which 'side' of the circle the tangent is wanted.

[jfc4120]

I am new to freecad and python. And yes I know how to find tangent. It would work except for another thing:

Freecad doesn't have a snap for the intersection of two arcs or circles, but does for lines. I was hoping a "veteran" python person could write a macro to do both.

I have experience it other languages, but not python, at least yet. For example see this post:
https://forum.freecadweb.org/viewtopic.php?f=22&t=70341

[edwilliams16]

If you want to make more complicated 2D objects with arcs and lines and various dimensions, you should use the sketcher.
See https://owncloud.gwdg.de/index.php/s/eZ ... 9/download and https://owncloud.gwdg.de/index.php/s/eZ ... 9/download

It is of course possible to do all your geometry by hand, but as it gets more complicated, the trade-off is to use the more powerful tool.