Difference between revisions of "Complex conjugate"
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* <math>z + \overline z = 2 \mathrm{Re}(z)</math> where <math>\mathrm{Re}(z)</math> is the [[real part]] of <math>z</math>. | * <math>z + \overline z = 2 \mathrm{Re}(z)</math> where <math>\mathrm{Re}(z)</math> is the [[real part]] of <math>z</math>. | ||
* <math>z - \overline{z} = 2i \mathrm{Im}(z)</math> where <math>\mathrm{Im}(z)</math> is the [[imaginary part]] of <math>z</math>. | * <math>z - \overline{z} = 2i \mathrm{Im}(z)</math> where <math>\mathrm{Im}(z)</math> is the [[imaginary part]] of <math>z</math>. | ||
− | + | * If a complex number <math>z</math> is a root of a polynomial with real coefficients, then so is <math>\overline z</math>. | |
{{stub}} | {{stub}} | ||
[[Category:Number Theory]] | [[Category:Number Theory]] |
Revision as of 15:08, 28 August 2008
The complex conjugate of a complex number is the complex number
.
Geometrically, if is a point in the complex plane,
is the reflection of
across the real axis.
Properties
Conjugation is its own functional inverse and commutes with the usual operations on complex numbers:
.
. (
is the same as
)
. (
is the same as
)
It also interacts in simple ways with other operations on :
.
.
- If
for
,
. That is,
is the complex number of same absolute value but opposite argument of
.
where
is the real part of
.
where
is the imaginary part of
.
- If a complex number
is a root of a polynomial with real coefficients, then so is
.
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