F.4,,mathz,,,find the base radius of the cone.
2008-09-24 6:15 am
回答 (1)
2008-09-24 6:27 am
✔ 最佳答案
slant height (l) = 25cmtotal surface area (A) = πr^2 + πrl = 224π
i.e., πr^2 + 25πr = 224π
π(r^2 + 25r - 224) = 0
r^2 + 25r - 224 = 0
(r-7) (r+32) = 0 <--- by quad. equation
r=7 or r=-32 (rejected)
therefore, base radius of the cone is 7cm.
參考: me
收錄日期: 2021-04-13 16:06:04
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https://hk.answers.yahoo.com/question/index?qid=20080923000051KK02388