Notes
multiple semi-circles ii solution

Multiple Semi-Circles II

Solution by Lune

Using the calculation of the area of a semi-circular lune, the area of region $A$ is equal to the area of the union of regions $B$ and $C$. Similarly, the area of region $D$ is equal to the area of the union of regions $E$, $B$, and $C$, $F$. Therefore, the yellow and red regions have the same area.