Consider a lifeguard at a circular pool with diameter 40 meters. He must reach someone who is drowning on the exact opposite side of the pool, at position . The lifeguard swims with a speed 2 meters/second
and runs around the pool at speed of 6 meters/second. Find at what angle
the lifeguard should swim to reach the drowning person in the least amount
of time.

NOTE: You will need two facts from geometry: 1) Central Angle Theorem
(also known as Inscribed Angle Theorem), which tells you that if is the
center of the circle above, then the angle ∠ has measure 2; 2) The
formula for the arclength of a segment of a circle.