According to the vertical diameter theorem:
R & ampsup2r & ampsup2= 3 & ampsup2=9
Semicircular area = π r&; sup2/2
Area of small semicircle = π r&; sup2/2
∴ Shadow area s = (π r&; sup2/2)-(πr & amp; sup2/2)=(π/2)(R & amp; sup2r & ampsup2)=9π/2