棱长为a各面均为等边三角形S-ABC的底面积怎么求?的底面积怎么求?高呢
\u5df2\u77e5\u68f1\u957f\u4e3aa\uff0c\u5404\u9762\u5747\u4e3a\u7b49\u8fb9\u4e09\u89d2\u5f62\u7684\u56db\u9762\u4f53s-abc,\u6c42\u5b83\u7684\u8868\u9762\u79ef\uff1f\u8fb9\u957f\u4e3aa\u7684\u7b49\u8fb9\u4e09\u89d2\u5f62\u9762\u79ef=½\u5e95\u00d7\u9ad8=½\uff08a\u00d7\u221a3/2a\uff09=\u221a3/4a²
\u56db\u9762\u4f53\u8868\u9762\u79ef=\u221a3a²
\u8fde\u7ed3AO\u5e76\u5ef6\u957f\uff0c\u4ea4BC\u4e8eD\uff0c\u8fde\u7ed3SD\uff0c
\u4fa7\u9762\u79ef\u662f\u5e95\u9762\u79ef\u76842\u500d,\uff0c\u25b3SBC\u548c\u25b3ABC\u5171\u7528\u5e95\u8fb9BC\uff0c
S\u25b3SBC=2S\u25b3ABC/3\uff0c\uff08\u4fa7\u9762\u79ef\u5e94\u662f\u4fa7\u9762\u4e09\u4e2a\u4e09\u89d2\u5f62\u9762\u79ef\uff09\uff0c
SD=2AD/3\uff0c
\u8bbeAD=x,
ODx/3,
SD=2x/3,
\u6839\u636e\u52fe\u80a1\u5b9a\u7406\uff0c
SO^2+OD^2=SD^2,
x=3\u221a3\uff0c
AD=3\u221a3\uff0c
SD=2\u221a3\uff0c
BD=\u221a3AD/3=3\uff0c
BC=6\uff0c
S\u25b3ABC=BC*AD/2=9\u221a3\uff0c
S\u25b3SBC=SD*BC/2=2\u221a3*6/2=6\u221a3\uff0c
\u2234\u8868\u9762\u79ef=6\u221a3*3+9\u221a3=27\u221a3\u3002
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