Orientation of angle between lines
This has been bugging me for a while, and I tend to forget the solution from one time to another, so at least this will serve as a note to self.
Whenever I want to mark an angle between two lines, it never seems to appear where I intended. I've come to realise that the position appears to be dependent on the direction of the line. Here's an example:
The four lines are defined as going in different directions, hence the angles end up differently in each case. Limiting the blue angles to 0°–180° just flips them over to the green side.
Let"s say I want to mark all the straight angles inside the resulting rectangle, i.e. getting v13 and v42 to join v21 and v34. Is there a way of achieving this without superimposing four additional lines going in opposite directions?