已知一个圆锥的底面半径为3cm,高为4cm,则这个圆锥的侧面积是( ) A.5πcm 2 B.10πcm 2 C 如图,圆锥的底面半径为3cm,高为4cm,那么这个圆锥的侧面...
\u5df2\u77e5\u5706\u9525\u7684\u5e95\u9762\u7684\u534a\u5f84\u4e3a3cm\uff0c\u9ad8\u4e3a4cm\uff0c\u5219\u5b83\u7684\u4fa7\u9762\u79ef\u4e3a A\uff0e15\u03c0cm 2 B\uff0e16\u03c0cm 2 C\uff0e19\u03c0cm 2 DA \u5206\u6790\uff1a\u6839\u636e\u5706\u9525\u7684\u5e95\u9762\u534a\u5f84\u548c\u9ad8\u6c42\u51fa\u5706\u9525\u7684\u6bcd\u7ebf\u957f\uff0c\u518d\u6839\u636e\u5706\u9525\u7684\u5e95\u9762\u5468\u957f\u7b49\u4e8e\u5706\u9525\u7684\u4fa7\u9762\u5c55\u5f00\u6247\u5f62\u7684\u5f27\u957f\uff0c\u6700\u540e\u5229\u7528\u6247\u5f62\u7684\u9762\u79ef\u8ba1\u7b97\u65b9\u6cd5\u6c42\u5f97\u4fa7\u9762\u79ef\uff0e\u89e3\uff1a\u7531\u52fe\u80a1\u5b9a\u7406\u5f97\uff1a\u5706\u9525\u7684\u6bcd\u7ebf\u957f= \u2235\u5706\u9525\u7684\u5e95\u9762\u5468\u957f\u4e3a2\u03c0r=2\u03c0\u00d73=6\u03c0\uff0c\u2234\u5706\u9525\u7684\u4fa7\u9762\u5c55\u5f00\u6247\u5f62\u7684\u5f27\u957f\u4e3a6\u03c0\uff0c\u2234\u5706\u9525\u7684\u4fa7\u9762\u79ef\u4e3a\uff1a \u00d76\u03c0\u00d75=15\u03c0\uff0e\u6545\u9009A\uff0e
\u7531\u4e8e\u5706\u9525\u7684\u5e95\u9762\u534a\u5f84\uff0c\u9ad8\uff0c\u6bcd\u7ebf\u7ec4\u6210\u76f4\u89d2\u4e09\u89d2\u5f62\uff0c\u6240\u4ee5\u7531\u52fe\u80a1\u5b9a\u7406\u77e5\uff1a\u6bcd\u7ebfl= 3 2 + 4 2 =5\uff0c\u2234\u5706\u9525\u7684\u4fa7\u9762\u79efS= 1 2 l\uff082\u03c0r\uff09=\u03c0rl=15\u03c0cm 2 \uff0e\u6545\u9009B\uff0e
∵圆锥的底面半径为3cm,高为4cm, ∴圆锥的母线长为5cm, ∴圆锥的侧面积为π×3×5=15πcm 2 , 故选C. |
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