发布时间:2025-01-22 21:51:34
井沿是圆环状,测内外直径,求出内外半径,大圆减小圆是圆环面积,再乘以井的深度,就是所需混凝土的体积。
delipow 德力普 5号充电电池 12v 1500mah 6粒装充电器详细介绍
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