A 7m ladder against a wall is shown when the foot of the ladder starts to slip away from the wall at 0.1 meters per second.

1. Find the rate at which the top of the ladder slides down the wall

2. Find this rate when:

a) the foot of the ladder is 3m away from the wall

b) the top is 4m above the ground

This question has me a little confused. I think Pythagoras is involved to some extent, but i really have no idea how to get the answer even started. If anyone could provide some assistance, that would be great.