设存在两个复数z₁,z₂,即 z₁=a₁+b₁i,z₂=a₂+b₂i ,证明|z1.z2|=|z1|.|z2|
推导过程:
z1.z2= (a₁+b₁i)(a₂+b₂i)= (a₁a₂-b₁b₂)+(a₁b₂+a₂b₁)i
∣z1.z2|²=(a₁a₂-b₁b₂)²+(a₁b₂+a₂b₁)²=(a₁a₂)²+(b₁b₂)²+(a₁b₂)²+(a₂b₁)²
=a₁²(a₂²+b₂²)+b₁²(b₂²+a₂²)
=(a₁²+b₁²)(a₂²+b₂²)
=∣z1|².∣z2|²=(|z1|.|z2|)²
说明:可以依次证明多个复数相乘的模=各个复数的模相乘