Figure 5
Once again, the key here is to add to the figure. And in this case, as so often
when there’s a circle, what you should add is radii. The equilateral triangles
tell you that the central angles are 60° and 120°.
In Figure 5, rectangle ABCD is inscribed in a circle. If the radius of the
circle is 1 and AB = 1, what is the area of the shaded region?