ewier22
幼苗
共回答了13个问题采纳率:76.9% 举报
(Ⅰ)详见解析; (Ⅱ) 点D到平面AEC的距离为
![](https://img.yulucn.com/upload/e/ea/eea8808aebfc2403a0d3fb27d33a31d7_thumb.jpg)
.
试题分析:(Ⅰ)求证EO⊥平面ABCD,只需证明
![](https://img.yulucn.com/upload/a/78/a78938abcfa4707e4065e14a04dfa96f_thumb.jpg)
垂直平面
![](https://img.yulucn.com/upload/8/48/8489a1ab41dffd599f97ea7ef30ad034_thumb.jpg)
内的两条直线即可,注意到
![](https://img.yulucn.com/upload/5/2d/52d246b660ce70a8aad5f3bb9d9ec29b_thumb.jpg)
,则
![](https://img.yulucn.com/upload/6/62/662077c8e9bb8ceb7c2c8ff96d91a372_thumb.jpg)
为等腰直角三角形,
![](https://img.yulucn.com/upload/3/40/3406bcd1934fb0fade2fd8156275cdac_thumb.jpg)
是
![](https://img.yulucn.com/upload/3/2f/32fcf3f7afab3909aaf696b288d6b74c_thumb.jpg)
的中点,从而得
![](https://img.yulucn.com/upload/9/c5/9c5373200eb0b629851d91dd0b187338_thumb.jpg)
,由已知可知
![](https://img.yulucn.com/upload/d/27/d276c57ce0b88a609b05e7aa15ad06ae_thumb.jpg)
为边长为2的等边三角形,可连接CO,利用勾股定理,证明EO⊥CO,利用线面垂直的判定,可得EO⊥平面ABCD;(Ⅱ)求点D到平面AEC的距离,求点到平面的距离方法有两种,一.垂面法,二.等体积法,此题的体积容易求,且
![](https://img.yulucn.com/upload/6/db/6db05cae1393dcc3fabbd3832dcd2c58_thumb.jpg)
的面积也不难求出,因此可利用等体积,即
![](https://img.yulucn.com/upload/4/b2/4b2259a10cf6da09951eebe7303bc896_thumb.jpg)
,从而可求点D到面AEC的距离.
试题解析:(Ⅰ)连接CO.
∵
![](https://img.yulucn.com/upload/5/2d/52d246b660ce70a8aad5f3bb9d9ec29b_thumb.jpg)
,∴△AEB为等腰直角三角形.1分
∵O为AB的中点,∴EO⊥AB,EO=1.2分
又∵四边形ABCD是菱形,∠ABC=60°,
∴△ACB是等边三角形,
∴CO=
![](https://img.yulucn.com/upload/1/55/15584da02e20752d87c11d953ec07837_thumb.jpg)
. 3分
又EC=2,∴EC
2 =EO
2 +CO
2 ,∴EO⊥CO.4分
又CO⊂平面ABCD,EO
![](https://img.yulucn.com/upload/8/f1/8f19e94744555a56e8cb97055a15bdee_thumb.jpg)
平面ABCD,∴EO⊥平面ABCD.6分
(Ⅱ)设点D到平面AEC的距离为h.
∵AE=
![](https://img.yulucn.com/upload/0/87/0878d57e1e2fb6d49ea36bcae8eed2e4_thumb.jpg)
,AC=EC=2,∴S
△ AEC =
![](https://img.yulucn.com/upload/6/47/647a5c2f854df6c2d645c6ea46fea595_thumb.jpg)
.8分
∵S
△ ADC =
![](https://img.yulucn.com/upload/1/55/15584da02e20752d87c11d953ec07837_thumb.jpg)
,E到平面ACB的距离EO=1,V
D -AEC =V
E -ADC ,9分
∴S
△ AEC ·h=S
△ ADC ·EO,∴h=
![](https://img.yulucn.com/upload/e/ea/eea8808aebfc2403a0d3fb27d33a31d7_thumb.jpg)
,11分
∴点D到平面AEC的距离为
![](https://img.yulucn.com/upload/e/ea/eea8808aebfc2403a0d3fb27d33a31d7_thumb.jpg)
. 12分
1年前
2