1. The problem statement, all variables and given/known data A right-angle is drawn on a sheet of paper. A ruler , which always remains perpendicular to the bisectrix of this angle moves over the paper with a speed 10cm/sec. The ends of the ruler intersect the sides of the angle. What are the speeds along the sides of the angle of their points of intersection with the ruler? 2. Relevant equations 3. The attempt at a solution I'm not asking anyone to give me a solutions I am just having difficulty picturing the physical scenario described in the question 1) Am I right to assume it means a right angle with legs parallel to the sides of the paper? 2) I don't understand what bisectrix means if not bisector and if so then how is the ruler perpendicular to the bisectrix and what is the bisectrix?