已知单位向量[img=10x19]1803dc6faf641de.png[/img],[img=8x24]1803dc6fb874b5c.png[/img]的夹角为45°，[img=49x26]1803dc6fc111356.png[/img]与[img=10x19]1803dc6fc9b3d41.png[/img]垂直，则k=__________.
A: [img=25x48]1803dc6fd28d824.png[/img]
B: 3
C: [img=25x48]1803dc6fdb88056.png[/img]
D: [img=34x48]1803dc6fe4bf6df.png[/img]
A: [img=25x48]1803dc6fd28d824.png[/img]
B: 3
C: [img=25x48]1803dc6fdb88056.png[/img]
D: [img=34x48]1803dc6fe4bf6df.png[/img]
举一反三
- 已知单位向量[img=10x19]1803dc6faf641de.png[/img],[img=8x24]1803dc6fb874b5c.png[/img]的夹角为45°，[img=49x26]1803dc6fc111356.png[/img]与[img=10x19]1803dc6fc9b3d41.png[/img]垂直，则k=__________. 未知类型：{'options': ['', '3', '', ''], 'type': 102}
- 若X ~ N(3,[img=18x22]1803392546fb4bb.png[/img] ) ，且P{X[img=14x21]180339254fafce9.png[/img]6}=0.9 ，则P{X<0}= ．
- 设随机变量X的密度函数为[img=213x68]17e441f39920bf6.png[/img],则[img=111x43]17e441f3a2f722f.png[/img] A: 1/6 B: 1/3 C: 5/6 D: 1/2
- 设随机变量X的密度函数为[img=213x68]17e0acb7b0cf40c.png[/img],则[img=111x43]17e0acb7bb65f3a.png[/img] A: 1/6 B: 1/3 C: 5/6 D: 1/2
- 设随机变量[img=75x25]1802d5ab02ff46a.png[/img]，且已知 E[(X - 1)(X + 2)] = 6，则[img=30x19]1802d5ab0aa816f.png[/img] A: 1 B: 2 C: 3 D: 4