1. The two short entities need to be parrallel and symetrical to the construction line.

But I'm not sure how to do. I keep trying different ways but it never works.

2. I need the circle to be free to rotate, but there must be an relation not allowing it.

How do I get the relations to display so I can eliminate ?

thank you, Frank

Hello,

I run with relations turned on so they're always shown while sketching.

Relate your two lines as equal and parallel.

Draw a construction line to the arc's endpoints (it's not a circle).

Relate either line perpendicular to the construction line:

This is still under defined, but the lines with rotate with the arc:

Kevin