In the diagram, two circles are centred at . The smaller circle has a radius of 1 and the larger circle has a radius of 3. Points and are placed on the larger circle so that the areas of the two shaded regions are equal.
If , what is the value of ?
, 2022
Solutions — 2
Solution 1
Since the shaded regions are equal, then when the unshaded sector
in the small circle is shaded, the area of the now fully shaded sector
of the larger circle must be equal to the area of the smaller
circle.
[[IMAGE0]]
The smaller circle has radius 1 and so has area . The larger circle has radius 3 and so has area . This means that the area of the shaded sector in the larger circle has area , which means that it must be of the larger circle. This means that must be of a complete circle, and so POQ = x = 40$.

Solution 2
Since the shaded regions are equal in area, then when the
unshaded sector in the small circle is shaded, the area of the now fully
shaded sector of the larger circle must be equal to the area of the
smaller circle.
[[IMAGE0]]
The smaller circle has radius 1 and so it has area . The larger circle has radius 3 and so it has area . This means that the area of the shaded sector in the larger circle is , which means that it must be of the larger circle. This means that must be of a complete circular angle, and so POQ = x = 40$.
