Problems about constraints, and dimensions

Do librecad have 'constraints' functions?
I want to draw a line that one end point coincides with a circle, while another side keeps in same position.

I remember librecad had both constraints and dimensions functions in the old version.
something like I can set the constraints of lines by clicking them while pressing the control buttom, or after seting the dimensions of lines, I can click the label to change the length of the line or the distance between this line and other line.

I haven't use this application for many years, this app changes a lot.
your answers are appriciated

'I remember librecad had both constraints and dimensions functions in the old version.'
Are you  sure you are talking about LibreCAD? I have never read about constraints with LibreCAD. There is Tools - Modify - Properties where you can edit some values, depending on the kind of entity, but probably not to the extent you expect.

You can stretch the endpoint of a line to a different position by clicking on the line, thus highlighting it, grab it at one of the small square handles and pull it elsewhere. If you want to put it on a circle, have 'Snap on Entity' activated.
Alternatively you can use Tools - Modify - Stretch.

Hello!

I am sure i have also managed to use this function previously.
However i dont know if contstraints is the correct term.

That when i move a line, the other follows, keeping the snap-location.