  he
figure on the right is a circle with radius a.
Its equation is x2
+ y2
= a2.
Point P is located along the circumference at some angle 
measured counterclockwise from the x-axis. Point Q
is located exactly 
radians (180 degrees) beyond P.
By inspection, we ascertain that PQ = 2a and
PQ is the longest line segment that will fit within the figure. The
angle |
