You are walking to a bus stop at a right-angle corner. You move north at a rate of 2 m/sec and
are 20 m south of the intersection. The bus travels west at a rate of 10 m/sec away from the
intersection – you have missed the bus! What is the rate at which the angle between you and
the bus is changing when you are 20 m south of the intersection and the bus is 10 m west of the
intersection?