訓(xùn)3
平陸灘母母擁之一全使陸灘牡母嚦鸞ゼ喲碩獠枯的咳Ｒ耙恍?
訓(xùn)懦
()ABC校A(5-1)B(-17)C(12)(1)BC系
AM某;(2)CAB平AD某;(3)cosABC值.
探
[1]圖知平ABCDA1B1C1D1牡妾〢BCD危搖C1CB=C1CD=BCD.
(1)證C1CBD.
(2) 值為時使A1C平C1BD?證.
圖要榭加χ?jǐn)澜堑约鍘讏D蔚慕.
知識校證寮感的粗扁，使使證眉.
訓(xùn)強(qiáng)目械位霉系系嗷プ疽供慕薪塹系.
敕絘b a·b=0證直嘰直只要證直叨應(yīng)為慵?
(1)證 =a, =b, =c,�，|a|=|b| 杉薪為齲 =a-b =c(a-b)=c·a-c·b=|c|·|a|cos-|c|·|b|cos=0,C1CBD.
(2)猓菏笰1C平C1BD只證A1CBDA1CDC1
=(a+b+c)·(a-c)=|a|2+a·b-b·c-|c|2=|a|2-|c|2+|b|·|a|cos-|b|·|c|·cos=0,
|a|=|c|時A1CDC1同證|a|=|c|時A1CBD
=1時A1C平C1BD.
[2]圖直ABCA1B1C1ABC校CA=CB=1BCA=90°AA1=2MN直A1B1A1A械.
(1) 某;
(2)cos< >值;
(3)證A1BC1M.
圖要榭夾的峰幾.
錛賭?
知識校墻恰目占直系O-xyz,業(yè).
訓(xùn)墻系螅確業(yè).
敕揭祒Oy詰ABC輳荒Ｒ襯?
(1)猓和糃為原憬ㄕ賈畢礝-xyz.
茫B(010)N(101)
| |= .
(2)猓好1(102)C(000)B1(012).
= =(012)
=1×0+(-1)×1+2×2=3
| |= (3)證茫C1(002)M( )
A1BC1M.
1.時一要平啤銑傘紙缺浠蝗墳僥搞，謀實識.位轉(zhuǎn)薪系思.
2.泄齲直影薪塹.直證拇直平;募薪槍式途牘秸賈邊的夾角?
3.每占寮敢簧奧固剿?/p>
(1)要什么知識?要玫些?
(2)要欠知?未知欠知轉(zhuǎn)傻直穎示?
(3)要直知轉(zhuǎn)傻示欠直母未知示?些未知知轉(zhuǎn)瀉喂系?
(4)丫示�，艿玫要�?
2018煽2018爍嚦時/
2018指希2018爍嚦指
