Tuesday, 22 April 2014

algebra precalculus - Proving |z1z2|=|z1||z2| using exponential form of a Complex Number



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|


No comments:

Post a Comment

real analysis - How to find limhrightarrow0fracsin(ha)h

How to find lim without lhopital rule? I know when I use lhopital I easy get $$ \lim_{h\rightarrow 0}...