用铁皮做一个容积为的圆柱形有盖桶,证明当圆柱的高等于底面直径时,所使用的铁皮面积最小。
设圆柱形的底面半径为高为则
所用铁皮面积
令
于是由实际问题得,存在最小值,即当圆柱的高等于地面直径时,所使用的铁皮面积最小。
Goods are carried by several of transport--on road or rail, by sea or air.
You can _____ some bottles of wine, or some chocolates, or a bunch of flowers.
A campus emergency ______ occur at any time of the day or night, weekend, or holiday, with little or no warning.
2002年新配方口服补液盐(ORS)溶液的张力是
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