高等代數與解析幾何習題解答 第二版 課后答案 陳志杰[1]

1、???????1???????1.?????????ABCD?A1B1C1D1E?F????BC?C1D1???.???→AB=?→a??→AD=?→b??→AA1=?→c.???→a?→b?→c??????:(1)??→AC1(2)??→BD1(3)?→AF(4)??→EF.ABDCA1B1D1C1FE?→a?→c?→b?1???:(1)????→BC=??→AD??→CC1=??→AA1??→AC1=??→AB??→BC??→CC1

2、????→AC1=?→a?→b?→c.(2)????→BD1=??→BD??→DD1???→BD=??→AD???→AB=?→b??→a??→DD1=??→AA1.????→BD1=?→b??→a?→c.(3)?→AF=??→AD??→DD1??→D1F???→DD1=??→AA1??→D1F=12???→D1C1=12??→AB1???????3??:???→AL??→BM??→CN?????????????????????????.

3、??→AL=12(??→AB?→AC)??→BM=12(??→BA??→BC)??→CN=12(?→CA??→CB)??:?→AL??→BM??→CN=0.BLCNMA?4??BLCNMAO?5??5.?O?△ABC?????:?→OA??→OB??→OC=0.?:???ALBMCN?3???O???????.??→OA=23?→LA=?23?→AL??→OB=?23??→BM??→OC=?23??→CN????4??→OA??→OB?

4、?→OC=?23(?→AL??→BM??→CN)=0.6.????O?ABC???G?△ABC???.??→OA??→OB??→OC???????→OG.?:????→GO=?→GA?→AO??→GO=??→GB??→BO??→GO=??→GC??→CO.???5???→GA??→GB??→GC=0.??3??→GO=?→AO??→BO??→CO.??→OG=13(?→OA??→OB??→OC).7.?ABCDEF????????→AB