正弦电压[img=136x24]1803d4b8541f80a.jpg[/img]，其正确的相量表示式为 。
A: [img=64x31]1803d4b85e17d6f.jpg[/img]
B: [img=76x41]1803d4b869b56bf.jpg[/img]
C: [img=95x41]1803d4b874f7f5f.jpg[/img]
D: [img=95x41]1803d4b87f5b071.jpg[/img]
A: [img=64x31]1803d4b85e17d6f.jpg[/img]
B: [img=76x41]1803d4b869b56bf.jpg[/img]
C: [img=95x41]1803d4b874f7f5f.jpg[/img]
D: [img=95x41]1803d4b87f5b071.jpg[/img]
举一反三
- 设f(x)为连续函数，且 [img=217x49]18034a50d8b1b92.png[/img] 则[img=70x25]18034a50e196c62.png[/img] A: 5 B: 4 C: 0 D: -5
- 设正态分布N(0, 4)的分布函数为F(x)，则F’(x) = ( ). A: [img=73x63]1802f2c47707b95.png[/img] B: [img=86x65]1802f2c47feb07a.png[/img] C: [img=75x58]1802f2c4884644b.png[/img] D: [img=87x58]1802f2c48fffbbf.png[/img]
- 设正态分布N(0, 4)的分布函数为F(x)，则F’(x) = ( ). A: [img=73x63]1802f2a8aba67a6.png[/img] B: [img=86x65]1802f2a8b46de33.png[/img] C: [img=75x58]1802f2a8bcdd988.png[/img] D: [img=87x58]1802f2a8c497bb0.png[/img]
- 设正态分布N(0, 4)的分布函数为F(x)，则F’(x) = ( ). A: [img=73x63]18031e92d8d1247.png[/img] B: [img=86x65]18031e92e1612dc.png[/img] C: [img=75x58]18031e92e9c3836.png[/img] D: [img=87x58]18031e92f20200d.png[/img]
- 设随机变量X的概率密度为[img=172x58]1802fe3273041d3.png[/img]则使得F{X > a} = F{X < a}成立，则a为( ). A: 2-1/4 B: 21/4 C: 1/2 D: 1-2-1/4