If the angle BCD is a right angle, it is easy to answer, otherwise it cannot be answered.

Solution: Turn on AC, then the shadow is divided into half petals and oblique triangles.

Half-leaf area: 3.14× 40×1/4-40× 40 ÷ 2 =1256-800 = 456 (square centimeter).

Oblique triangle area: 70×40÷2= 1400 (square centimeter)

Shadow area: 456+ 1400= 1856 (square centimeter)