C\u00e2u 1:<\/b>\u00a0Trong kh\u00f4ng gian Oxyz , cho vect\u01a1\u00a0a\u2192<\/i>\u00a0= (2; 1; -2) . T\u00ecm t\u1ecda \u0111\u1ed9 c\u1ee7a c\u00e1c vect\u01a1\u00a0b\u2192<\/i>\u00a0c\u00f9ng ph\u01b0\u01a1ng v\u1edbi vect\u01a1\u00a0a\u2192<\/i>\u00a0v\u00e0 c\u00f3 \u0111\u1ed9 d\u00e0i b\u1eb1ng 6<\/p>\n

<\/p>\n

C\u00e2u 2:<\/b>\u00a0Trong kh\u00f4ng gian Oxyz, cho hai vect\u01a1<\/p>\n

<\/p>\n

V\u1edbi nh\u1eefng gi\u00e1 tr\u1ecb n\u00e0o c\u1ee7a m th\u00ec sin(a\u2192<\/i>,\u00a0b\u2192<\/i>) \u0111\u1ea1t gi\u00e1 tr\u1ecb l\u1edbn nh\u1ea5t<\/p>\n

A. m=1 \u00a0\u00a0\u00a0 C. m=-8<\/p>\n

B. m=1 ho\u1eb7c m=-8\u00a0\u00a0\u00a0D. Kh\u00f4ng t\u1ed3n t\u1ea1i m th\u1ecfa m\u00e3n.<\/p>\n

C\u00e2u 3:<\/b>\u00a0Trong kh\u00f4ng gian Oxyz , g\u1ecdi \u03c6 l\u00e0 g\u00f3c t\u1ea1o b\u1edfi hai vect\u01a1\u00a0a\u2192<\/i>\u00a0= (4; 3; 1);\u00a0b\u2192<\/i>\u00a0= (-1; 2; 3). Trong c\u00e1c kh\u1eb3ng \u0111\u1ecbnh sau, kh\u1eb3ng \u0111\u1ecbnh n\u00e0o \u0111\u00fang?<\/p>\n

<\/p>\n

C\u00e2u 4:<\/b>\u00a0Trong kh\u00f4ng gian Oxyz , cho h\u00ecnh b\u00ecnh h\u00e0nh ABDC v\u1edbi A(0;0;0), B(1;-2;3), D(3;1;-4). T\u1ecda \u0111\u1ed9 c\u1ee7a \u0111i\u1ec3m C l\u00e0:<\/p>\n

A. (4;-1;-1)\u00a0\u00a0\u00a0B. (2;3;-7)\u00a0\u00a0\u00a0C. (3\/2; 1\/2; -2)\u00a0\u00a0\u00a0D. (-2;-3;7)<\/p>\n

H\u01b0\u1edbng d\u1eabn gi\u1ea3i v\u00e0 \u0110\u00e1p \u00e1n<\/b><\/p>\n\n\n\n

1-C<\/td>\n

2-B<\/td>\n

3-A<\/td>\n

4-B<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n C\u00e2u 1:<\/b><\/p>\n Ta c\u00f3:<\/p>\n <\/p>\n M\u1eb7t kh\u00e1c hai vect\u01a1 n\u00e0y c\u00f9ng ph\u01b0\u01a1ng n\u00ean ta c\u00f3:<\/p>\n <\/p>\n T\u1eeb \u0111\u00f3 ta suy ra<\/p>\n <\/p>\n V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n t\u00ecm l\u00e0 C.<\/p>\n L\u01b0u \u00fd. \u0110\u00e1p \u00e1n D l\u00e0 sai, do sai l\u1ea7m trong t\u00ednh \u0111\u1ed9 d\u00e0i c\u1ee7a vect\u01a1\u00a0a\u2192<\/i>\u00a0:<\/p>\n <\/p>\n M\u00e0 hai vect\u01a1 n\u00e0y c\u00f9ng ph\u01b0\u01a1ng n\u00ean ta c\u00f3:<\/p>\n <\/p>\n C\u00e2u 2:<\/b><\/p>\n V\u1edbi m\u1ecdi c\u1eb7p vect\u01a1<\/p>\n <\/p>\n D\u1ea5u b\u1eb1ng x\u1ea3y ra khi v\u00e0 ch\u1ec9 khi hai vect\u01a1 n\u00e0y vu\u00f4ng g\u00f3c. \u0110i\u1ec1u \u0111\u00f3 t\u01b0\u01a1ng \u0111\u01b0\u01a1ng v\u1edbi \u0111i\u1ec1u ki\u1ec7n :<\/p>\n a\u2192<\/i>.b\u2192<\/i>\u00a0= 1.(-5) + m.(m + 1) + (2m – 1).3 = 0<\/p>\n <\/p>\n Ch\u1ecdn B.<\/p>\n N\u1ebfu ch\u00fang ta suy ngh\u0129 sai l\u00e0: \u2018\u2018 sin(a\u2192<\/i>,\u00a0b\u2192<\/i>) \u0111\u1ea1t gi\u00e1 tr\u1ecb l\u1edbn nh\u1ea5t khi v\u00e0 ch\u1ec9 khi g\u00f3c gi\u1eefa hai vect\u01a1 \u0111\u00f3 l\u1edbn nh\u1ea5t \u2019\u2019 th\u00ec khi \u0111\u00f3 g\u00f3c gi\u1eefa hai vect\u01a1 b\u1eb1ng 180o<\/sup>\u00a0, do \u0111\u00f3 t\u1ed3n t\u1ea1i s\u1ed1 k \u00e2m sao cho :<\/p>\n <\/p>\n H\u1ec7 n\u00e0y v\u00f4 nghi\u1ec7m v\u00e0 d\u1eabn \u0111\u1ebfn ta ch\u1ecdn \u0111\u00e1p \u00e1n l\u00e0 D.<\/p>\n C\u00e2u 3:<\/b><\/p>\n Ta c\u00f3<\/p>\n <\/p>\n Suy ra<\/p>\n <\/p>\n V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/p>\n \n <\/div>\n<\/div>\n <\/p>\n","protected":false},"excerpt":{"rendered":" C\u00e2u 1:\u00a0Trong kh\u00f4ng gian Oxyz , cho vect\u01a1\u00a0a\u2192\u00a0= (2; 1; -2) . T\u00ecm t\u1ecda \u0111\u1ed9 c\u1ee7a c\u00e1c vect\u01a1\u00a0b\u2192\u00a0c\u00f9ng ph\u01b0\u01a1ng v\u1edbi vect\u01a1\u00a0a\u2192\u00a0v\u00e0 c\u00f3 \u0111\u1ed9 d\u00e0i b\u1eb1ng 6 C\u00e2u 2:\u00a0Trong kh\u00f4ng gian Oxyz, cho hai vect\u01a1 V\u1edbi nh\u1eefng gi\u00e1 tr\u1ecb n\u00e0o c\u1ee7a m th\u00ec sin(a\u2192,\u00a0b\u2192) \u0111\u1ea1t gi\u00e1 tr\u1ecb l\u1edbn nh\u1ea5t A. m=1 \u00a0\u00a0\u00a0 C. m=-8 B. m=1 […]<\/p>\n","protected":false},"author":3,"featured_media":28547,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_mi_skip_tracking":false,"tdm_status":"","tdm_grid_status":""},"categories":[157],"tags":[1450,1448],"yoast_head":"\n