13.已知复数z=$\frac{1-i}{1+i}$(i为虚数单位),则z的虚部是( )
| A. | 1 | B. | -1 | C. | 0 | D. | -i |
12.已知定义域为R的偶函数f(x)在[0,+∞)上是增函数,若实数a满足f(log2a)+f(log0.5a)≤2f(1),则a的最小值是( )
| A. | $\frac{1}{2}$ | B. | 1 | C. | $\frac{3}{2}$ | D. | 2 |
10.已知X~N(μ,σ2)时,P(μ-σ<X≤μ+σ)=0.6826,P(μ-2σ<X≤μ+2σ)=0.9544,P(μ-3σ<X≤μ+3σ)=0.9974,则$\int_3^4{\frac{1}{{\sqrt{2π}}}}{e^{-\frac{{{{({x-1})}^2}}}{2}}}$dx=( )
| A. | 0.043 | B. | 0.0215 | C. | 0.3413 | D. | 0.4772 |
9.等差数列{an}的前n项和为Sn,且a3=5,则S5=( )
| A. | 3 | B. | 5 | C. | 9 | D. | 25 |
8.已知复数z=$\frac{3-i}{2+i}$(i为虚数单位),则|z|=( )
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| A. | $\sqrt{2}$ | B. | 2 | C. | $\sqrt{3}$ | D. | $\frac{3}{2}$ |