S阴影=S(半圆AC)+S(半圆BC)+S(三角形ABC)-S(半圆AB)
=1/2*3.14*(AC/2)^2+1/2*3.14*(BC/2)^2+20-1/2*3.14*(AB/2)^2
=1/2*3.14*1/4*(AC^2+BC^2-AB^2)+20
=0+20,(因为AC^2+BC^2=AB^2)
=20.
即阴影面积=20.
S阴影=S(半圆AC)+S(半圆BC)+S(三角形ABC)-S(半圆AB)
=1/2*3.14*(AC/2)^2+1/2*3.14*(BC/2)^2+20-1/2*3.14*(AB/2)^2
=1/2*3.14*1/4*(AC^2+BC^2-AB^2)+20
=0+20,(因为AC^2+BC^2=AB^2)
=20.
即阴影面积=20.