Difference between revisions of "Complex conjugate"
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− | The '''conjugate''' of a [[complex number]] <math>z = a + bi</math> is <math>a - bi</math>, denoted by <math>\overline{z}</math>. Geometrically, <math>\overline z</math> is the [[reflect]]ion of <math>z</math> across the [[real axis]] if both points were plotted in the [[complex plane]]. | + | The '''conjugate''' of a [[complex number]] <math>z = a + bi</math> is <math>a - bi</math>, denoted by <math>\overline{z}</math>. Geometrically, <math>\overline z</math> is the [[reflect]]ion of <math>z</math> across the [[real axis]] if both points were plotted in the [[complex plane]].For all polynomials with real coefficients, if a complex number <math>z</math> is a root of the polynomial its conjugate <math>\overline{z}</math> will be a root as well. |
==Properties== | ==Properties== | ||
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Revision as of 17:26, 25 January 2020
The conjugate of a complex number is
, denoted by
. Geometrically,
is the reflection of
across the real axis if both points were plotted in the complex plane.For all polynomials with real coefficients, if a complex number
is a root of the polynomial its conjugate
will be a root as well.
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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