• YOU can help the next generation of students in the community!
    Share your trial papers and notes on our Notes & Resources page

Complex Numbers Help (1 Viewer)

untouchablecuz

Active Member
Joined
Mar 25, 2008
Messages
1,693
Gender
Male
HSC
2009
Why does:

|iz| = |i||z| = |z|

or

|bz| = |b||z| = |z|

What happens to |i| or |b| at the end?

Thanks for any help (I just started 4 unit today).
 

gurmies

Drover
Joined
Mar 20, 2008
Messages
1,209
Location
North Bondi
Gender
Male
HSC
2009
|zi| = |z||i|
= |z|
I have also recently started 4 unit, so my explanation may be dodgy and at worst, wrong. Not sure why at this particular point in time, but you know that |z1| x |z2| = |z1z2|. In words, the modulus of a complex number multiplied by the modulus of another complex number is equal to the modulus of the products of these complex numbers. Anyway assume z is any complex number x + iy. You know that in the case of "i" x = 0 and y = 1. Therefore it's modulus is 1. So in essence, you are writing 1 x |z| = |z|. As for the b, not sure what's going on there? Logically the modulus of b has to be 1.
 
Last edited:

tabbaa

Member
Joined
Oct 7, 2007
Messages
75
Gender
Male
HSC
2008
Hey OP

When you multiply an complex number with i, it just means that you are rotating it 90 deg anti-clockwise.

The Mod doesn't change.
 

shaon0

...
Joined
Mar 26, 2008
Messages
2,029
Location
Guess
Gender
Male
HSC
2009
Hey guys,
I've proved this but have seemingly lost where i wrote the solution.
z=a+ib
Prove:
If (z)/(z-i) is real then z is imaginary.
 

shaon0

...
Joined
Mar 26, 2008
Messages
2,029
Location
Guess
Gender
Male
HSC
2009
shaon0 said:
Hey guys,
I've proved this but have seemingly lost where i wrote the solution.
z=a+ib
Prove:
If (z)/(z-i) is real then z is imaginary.
Anyone?
 

untouchablecuz

Active Member
Joined
Mar 25, 2008
Messages
1,693
Gender
Male
HSC
2009
shaon0 said:
Hey guys,
I've proved this but have seemingly lost where i wrote the solution.
z=a+ib
Prove:
If (z)/(z-i) is real then z is imaginary.
Scroll down to find it. :)
 

Cazic

Member
Joined
Aug 26, 2009
Messages
166
Gender
Male
HSC
2011
Hahaha, I was like wtf is untouchablecuz asking this for?
 

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top