Just imagining the mathematics SWAT team coming through the door and swatting the marker out of one of my physics profs' hands when they went from ydy/dx=x -> y

Just imagining the mathematics SWAT team coming through the door and swatting the marker out of one of my physics profs' hands when they went from ydy/dx=x -> ydy=xdx as if they were simply re-arranging a fraction, made me chuckle.