How to make blue lines black and how to constrain a shape to a circle

[whkiess]

I can't for the likes of me get this simple trapezoid to go black. I've tried all sorts of constraints but none seem to work. It's very simple: the top is 3.6mm long, the bottom is 6.5mm long, they are parallel and constrained at their midpoint with a distance of 3.1mm between them. Then I draw the lines at the diagonal edges and constrain them to be coincident by dragging the selection around the corners. But it still won't go black. What am I missing?

Once black, I want to move this trapezoid such that the bottom line's points are coincident with the inner circle, that the middle line of the trapezoid is aligned with the Y-Axis (or the bottom line is perpendicular to the Y-Axis, there's a construction line there to mark it). How do I make the trapezoids bottom end points coincident with the circle as described above?

This is what I currently have:

And this is roughly what I'm trying to achieve (but with black lines not blue)

Any suggestions from the gurus?

[davebYYPCU · Accepted solution]

Make the centre line of the trapizoid, coincident with the construction line.

make the end point of the low line coincident with inner circle, 

There is no need to get it to black - where it is now, - if you are then going to move it.

But to make it black where it is now, needs dimensions back to the Origin.

Might help....

[chrisplyler]

Doesn't have to be dimension to the Origin. Could be dimension to anything else that is already black. But might need that twice (x direction and y direction) to lock it in place.

If locking it in place doesn't make it black, then it's because the shape itself could still deform. Try adding an angle dimension on at least one of the corners.

[davebYYPCU]

Best practise to dimension from the Origin, 

can't deform with current dimensions and constraints, but could move.

[chrisplyler]

Ah... yes that appears to be true.

Could just edit the sketch, add a point in at a useful place, and make that point coincident to some other point that's already black.