Answer: Let the centers of three circles be O 1, O2, O3, as shown in the following figure.

Sector O 1O2O3 area: s 1 = n/360 π r? =60/360 π 1? =π/6。

Area of triangle O 1O2O3: S2=√3r? /4=√3/4。

The red area S3 = s1-s1= π/6-√ 3/4.

Shadow area S4 = s1+2s3 = π/6+2 (π/6-√ 3/4) = π/2-√ 3/2cm? .