Problem:
Prove |z1z2|=|z1||z2| where z1,z2 are Complex Numbers.
I tried to solve this using the exponential form of a Complex Number.
Assuming z1=r1eiθ1 and z2=r2eiθ2,
I got |z1z2|=|r1eiθ1×r2eiθ2|=|r1r2ei(θ1+θ2)|
Unfortunately I cannot think of how to proceed further. Any help would be greatly appreciated! Many thanks in anticipation!
Answer
|reiθ|=|r|
So
|z1|=|r1|
|z2|=|r2|
|z1z2|=|r1r2|
r1,r2 are real numbers and so |r1r2|=|r1||r2|=|z1||z2|
|z1z2|=|z1||z2|
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