Let S be an inertial reference system. Use Galileo’s velocity addition rule. (a) Suppos...

Let S be an inertial reference system. Use Galileo’s velocity addition rule.

(a) Suppose that is also an inertial reference system. [Hint: Use the definition in footnote 1.]

(b) Conversely, show that if is an inertial system, then it moves with respect to S at constant velocity.