Hi Peter,
it is a "work of art" and not 100% the standard:
- TechDraw14.png (12.19 KiB) Viewed 1845 times
Workflow:
- create a help-line (cyan) perpendicular to the top line through the right vertex
- create a second help-line (cyan) perpendicular to the first one.
- create the intersection vertex at the arc
- use TechDraw "Length dimension" selecting the first help-line and the vertex at the arc
- now the two help-lines can be erased
When creating a tool in Python, vertexes and lines can be calculated and created. But in Python there are only the same possibilitys to use the dimension commands as manually.