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为庆祝祖国六十华诞,某单位排练的节目需用到如图所示的扇形布扇,布扇完全打开后,外...
为庆祝祖国六十华诞,某单位排练的节目需用到如图所示的扇形布扇,布扇完全打开后,外侧两竹条AB,AC夹角为120°,AB的长为30cm,贴布部分BD的长为20cm,则贴布部分的面积约为
cm
2(π取3)
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