PLEASE Come In .I HOPE You Can Help Me!如图,△ABC的面积为1,分别取AC,BC两边的中点A1,B1,记四边形A1ABB1的面积为S1;再分别取A1C1,B1C的中点A2,B2,记四边形A2A1,B1B2的面积为S2;再分别取A2C,B2C的中点A3,B3,.,依次
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PLEASE Come In .I HOPE You Can Help Me!
如图,△ABC的面积为1,分别取AC,BC两边的中点A1,B1,记四边形A1ABB1的面积为S1;再分别取A1C1,B1C的中点A2,B2,记四边形A2A1,B1B2的面积为S2;再分别取A2C,B2C的中点A3,B3,.,依次类推.
(1)由已知,可求得S1=——,S2=——,S100=——;
(2)利用这一图形,计算3/(4的100次)+3/(4的101次)+3/(4的102次)+.+3/(4的200次)
可以酌情加分.
额 既然是中点
所以每次去中点 S 都乘以 1/4
即
S ABC = 4 S A1B1C
S AnBnC = 1/ 4的n次方
第二问
即等比数列求和
或
提出一个3/4的200次方
然后 括号内
4的100次方+4的99次方+.4+1
然后用 4的100次方 - 1/4 去除以 1- 1/4
最后 再乘上外面的 3/4的200次方
i don't know what you said, i didn't understand your writing.
(1)用S=ab*sinC/2公式易得:
S1=3/4
S2=3/4^2
S100=3/4^100
(2) 3/4^100+3/4^101+3/4^102+......+3/100^200
=(4^100-1)/4^199
注:(2)是用数列算的,用图形还没想到
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