a ladder stands against a wall, then it slides down. Describe the motion of the centre of the ladder while sliding!

the lenght of ladder is contant. when it is in the middle of sliding, it make a right angle triangle with the floor and wall, hence (the lenght of the ladder£^2  equal to (the lenght of floor to one end of the ladder)^2 + (the lenght of wall to the other end of ladder)^2. to simplify it will look like a^2 + b^2= constant^2.. which is circular motion.