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Paper 3
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Perplex
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Complex Numbers
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Complex conjugate
Solving complex equations
Complex conjugate
Complex Numbers

Complex conjugate

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The complex conjugate: ​z=a+bi⟹z∗=a−bi, its properties, and using it to simplify fractions with complex denominators.

Complex conjugates
AHL 1.12

The conjugate of a complex number ​z​ is the complex number with the same real component and the opposite imaginary component:

​
z=a+bi⇔z∗=a−bi🚫
​

Since the real components of ​z​ and ​z∗​ are the same, and the imaginary components are opposite, on the complex plane ​z∗​ is the reflection of ​z​ in the ​x​-axis.

Properties of the complex conjugate
AHL 1.12

The following properties hold for complex conjugates:

​
(z∗)∗=z🚫
​


​
(z±w)∗=z∗±w∗🚫
​


​
(zw)∗=z∗w∗🚫
​


​
(wz​)∗=w∗z∗​🚫
​
Fractions of complex numbers
AHL 1.12

Fractions with complex denominator can be made real using a process analogous to rationalizing the denominator. For a fraction with a complex denominator ​c+di, we multiply both the numerator and the denominator by the conjugate ​c−di​ to get the fraction in a more workable form:

​
z=c+dia+bi​​=c+dia+bi​⋅c−dic−di​​
​

This allows us to split ​z​ into its real and imaginary components.


Example

​
4−i3+2i​    ​=4−i3+2i​⋅4+i4+i​ =16+4i−4i+i212+11i−2​ =1710+11i​​
​

Nice work completing Complex conjugate, here's a quick recap of what we covered:

Skills covered

Mixed Practice

Exercises checked off

I'm Plex, here to help you understand this concept!
/
Complex Numbers
/
Complex conjugate
Solving complex equations
Complex conjugate
Complex Numbers

Complex conjugate

0 of 0 exercises completed

The complex conjugate: ​z=a+bi⟹z∗=a−bi, its properties, and using it to simplify fractions with complex denominators.

Complex conjugates
AHL 1.12

The conjugate of a complex number ​z​ is the complex number with the same real component and the opposite imaginary component:

​
z=a+bi⇔z∗=a−bi🚫
​

Since the real components of ​z​ and ​z∗​ are the same, and the imaginary components are opposite, on the complex plane ​z∗​ is the reflection of ​z​ in the ​x​-axis.

Properties of the complex conjugate
AHL 1.12

The following properties hold for complex conjugates:

​
(z∗)∗=z🚫
​


​
(z±w)∗=z∗±w∗🚫
​


​
(zw)∗=z∗w∗🚫
​


​
(wz​)∗=w∗z∗​🚫
​
Fractions of complex numbers
AHL 1.12

Fractions with complex denominator can be made real using a process analogous to rationalizing the denominator. For a fraction with a complex denominator ​c+di, we multiply both the numerator and the denominator by the conjugate ​c−di​ to get the fraction in a more workable form:

​
z=c+dia+bi​​=c+dia+bi​⋅c−dic−di​​
​

This allows us to split ​z​ into its real and imaginary components.


Example

​
4−i3+2i​    ​=4−i3+2i​⋅4+i4+i​ =16+4i−4i+i212+11i−2​ =1710+11i​​
​

Nice work completing Complex conjugate, here's a quick recap of what we covered:

Skills covered

Mixed Practice

Exercises checked off

I'm Plex, here to help you understand this concept!

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