如图所示,无限长直导线在P处弯成半径为[img=14x19]1803aa9d3a78fb8.png[/img]的圆,当通以电流[img=8x19]1803aa9d423e689.png[/img]时,则在圆心[img=14x19]1803aa9d4a677b3.png[/img]点的磁感应强度的大小为 [img=638x324]1803aa9d544c33a.png[/img]
A: [img=87x44]1803aa9d5ce7a96.png[/img]
B: [img=33x44]1803aa9d6569075.png[/img]
C: [img=26x44]1803aa9d6e3a6cf.png[/img]
D: [img=9x18]1803aa9d769eaee.png[/img]
E: [img=81x44]1803aa9d7f78f1c.png[/img]
A: [img=87x44]1803aa9d5ce7a96.png[/img]
B: [img=33x44]1803aa9d6569075.png[/img]
C: [img=26x44]1803aa9d6e3a6cf.png[/img]
D: [img=9x18]1803aa9d769eaee.png[/img]
E: [img=81x44]1803aa9d7f78f1c.png[/img]
举一反三
- 设X为随机变量,且E(X)= −1,Var(X)=3,则[img=136x31]1803b3be69ca3f3.png[/img] A: 18 B: 9 C: 30 D: 14
- 如图所示,无限长直导线在P处弯成半径为[img=14x19]1802ce3cb4be394.png[/img]的圆,当通以电流[img=8x19]1802ce3cbc893e1.png[/img]时,则在圆心[img=14x19]1802ce3cc44dff2.png[/img]点的磁感应强度的大小为 [img=638x324]1802ce3ccf12b07.png[/img] A: [img=87x44]1802ce3cd7e2cd6.png[/img] B: [img=33x44]1802ce3ce0081c3.png[/img] C: [img=26x44]1802ce3ce832635.png[/img] D: [img=9x18]1802ce3cf0930e6.png[/img] E: [img=81x44]1802ce3cf8a8cbd.png[/img]
- 下列函数的导数[img=281x27]1802f62346026a9.png[/img] A: g'(x)=3 B: g'(x)=-3 C: g'(x)=9 D: g'(x)=-9
- X为随机变量,E(X)=-1,D(X)=3,则[img=105x27]17de66c4ef75d99.png[/img] A: 18 B: 9 C: 30 D: 32
- (5切比雪夫不等式)设随机变量X的期望E(X)=μ,方差D(X)=[img=14x17]17e43703436673a.jpg[/img],利用切比雪夫不等式估计P{|X-E(X)|[img=30x16]17e437fbfd2e01c.jpg[/img]}>; () A: 1/9 B: 1/3 C: 8/9 D: 1