I would like
the North-East vertex of the blue square to be fixed at the
current position and the length of the sides of the blue squares
should stay the same as well.
How do I do that?
I want to rotate the blue rectangle around the North-East vertex.
Your blue rectangle should be constructed
North-East vertex will be the center of circles
of fixed width from where you will construct the other point:
The tools to use are : free value (to set the
radius), circle defined by center and radius, segment,
perpendicular line, intersection between line and circle.
It will require some searching... If can't find
how to, I will make an example for you.