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为增加绿化面积,某小区将原来正方形地砖更换为如图所示的正八边形植草砖,更换后,图...
为增加绿化面积,某小区将原来正方形地砖更换为如图所示的正八边形植草砖,更换后,图中阴影部分为植草区域,设正八边形与其内部小正方形的边长都为a,则阴影部分的面积为
.
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