设i是虚数单位,复数z=a+bi(-3≤a≤3,-3≤b≤3,

问题描述:

设i是虚数单位,复数z=a+bi(-3≤a≤3,-3≤b≤3,
则z的绝对值≤3的概率为

π/4.-3≤a≤3,-3≤b≤3在复平面上是正方形,面积是36,z的模≤3在复平面上是圆,面积是9π,9π/36=π/4.