Hi wolfhound,

Remember the "distance formula" ?

This is Pythagoras' Theorem using co-ordinates.

Just as on a clock, the hands are pivoted at the centre,

the hands are always the same length, but the point moves around the clock circumference. The circle circumference is the set ofallpoints that are the same distance from the centre.

If the centre co-ordinates are (0,0), this reduces to