Khan/khan-exercises — pull request #11724 by GalaxiaGuy (2012-01-20 20:18:03+00:00)
Title: Fix for issue #11624

#11624
#6156
#2803
#11242

Plus others probably...

quadrilateral_angles assumed that some quadrilaterals were trapezoids without proving it. This annotates the sides as being parallel and adds a note saying as much to the question. It does not do this for isosceles quadrilaterals or parallelograms since working this out from the information given is a good part of the question.

It doesn't do this terribly generically however. For a given quadrilateral only a single set of lines can be marked as parallel and it will only look right is the lines are nearly vertical or nearly horizontal. I believe it is still an improvement however.