发布时间:2019-08-09 14:57:38
=48/360πR²-48/360πr²
=48/360π(R²-r²)
=48/360π(5²-3²)
=48/360π×16
=32π/15
阴影面积为(48°/360°)×(πR²-πr²)=(2/15)×(5²π-3²π)=(2/15)×16π=(2/15)×16×3.14=6.7