1. In which direction is a rotation with a negative angle of rotation ?

Negative rotations are clockwise, positive rotations are anti-clockwise around the centre of rotation.

2. What is a half turn rotation?

A half turn rotation is a rotation of 180o.

3. How many points are invariant (do not move) under rotations?

There is only one invariant point under a rotation. That is the centre of rotation.

4. What happens if we rotate an object through an angle of 360o?

We get back to where we started from!