一:S影=S半圆-S下白=S半圆-(S△ABC-S扇形)
=BC²π/4÷2-12+AB²π×45/360
=3π-12+3π
=6π-12
=18.84-12
=6.84(cm²)
二、S△(乙+白)-S长方形=3
(m+4)×6÷2-4×6=3
3(m+4)=27
m=5(cm)
一:S影=S半圆-S下白=S半圆-(S△ABC-S扇形)
=BC²π/4÷2-12+AB²π×45/360
=3π-12+3π
=6π-12
=18.84-12
=6.84(cm²)
二、S△(乙+白)-S长方形=3
(m+4)×6÷2-4×6=3
3(m+4)=27
m=5(cm)