How big is $|z^w|$ compared to $|z|$?
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I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.
complex-analysis complex-numbers
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I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.
complex-analysis complex-numbers
Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47
One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52
add a comment |
up vote
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up vote
0
down vote
favorite
I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.
complex-analysis complex-numbers
I've found a nice way to write complex exponentiation, and when we look at that formula, $|z^w|$ and $Arg(z^w)$ become much more apparent. So using the formula, with what kind of proportionality can we describe $|z^w|$ compared to $|z|$? $$z^w = frac{|z|^{Re(w)}}{e^{Arg(z)Im(w)}}e^{(Arg(z)Re(w)+ln(|z|)Im(w))i}$$If $Re(w)$ is $0$, one can see that $Arg(z^w)$ is logarithmically proportional to $|z|$, but I do not know how to describe the proportionality of $Arg(z)$ compared to $|z^w|$, but I suspect one could say that $|z^w|$ is negatively exponentially proportional to $Arg(z)$ or something like that.
complex-analysis complex-numbers
complex-analysis complex-numbers
edited Nov 16 at 9:41
asked Nov 14 at 15:18
Nils Phillip Talgö
86
86
Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47
One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52
add a comment |
Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47
One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52
Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47
Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47
One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52
One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52
add a comment |
2 Answers
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Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.
By definition, $|z|=r$.
$z^w = z^{a+jb}$
= $z^a z^{jb}$
= $r^a e^{jatheta} r^{jb} e^{-theta b}$
We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.
This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.
Seems hard to simplify beyond this for the most general case.
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
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$$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$
But notice that the argument is not uniquely defined, you need to choose a branch.
Obviously, for real $w$,
$$|z^w|=|z|^w.$$
add a comment |
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
0
down vote
Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.
By definition, $|z|=r$.
$z^w = z^{a+jb}$
= $z^a z^{jb}$
= $r^a e^{jatheta} r^{jb} e^{-theta b}$
We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.
This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.
Seems hard to simplify beyond this for the most general case.
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
add a comment |
up vote
0
down vote
Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.
By definition, $|z|=r$.
$z^w = z^{a+jb}$
= $z^a z^{jb}$
= $r^a e^{jatheta} r^{jb} e^{-theta b}$
We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.
This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.
Seems hard to simplify beyond this for the most general case.
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
add a comment |
up vote
0
down vote
up vote
0
down vote
Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.
By definition, $|z|=r$.
$z^w = z^{a+jb}$
= $z^a z^{jb}$
= $r^a e^{jatheta} r^{jb} e^{-theta b}$
We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.
This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.
Seems hard to simplify beyond this for the most general case.
Let $z = re^{j theta}$, $w = a+jb$, and $j=sqrt{-1}$.
By definition, $|z|=r$.
$z^w = z^{a+jb}$
= $z^a z^{jb}$
= $r^a e^{jatheta} r^{jb} e^{-theta b}$
We know that $|e^{jab}|=1$ and also $|r^{jb}| =1$ because you can rewrite $r^{jb}=e^{jb'}$.
This leaves us with $|z^w| = r^a e^{-theta b}$. In other words, $|z^w| = |z|^{Re{w}} e^{-Im{w} cdot Arg{z}}$, where $Re$ and $Im$ denote the real and imaginary parts, respectively.
Seems hard to simplify beyond this for the most general case.
answered Nov 16 at 17:27
Aditya Dua
4906
4906
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
add a comment |
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
Yes, that is clear, but my question was how to describe that relation. In what kind of proportionality can one describe that?
– Nils Phillip Talgö
Nov 18 at 14:58
add a comment |
up vote
0
down vote
$$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$
But notice that the argument is not uniquely defined, you need to choose a branch.
Obviously, for real $w$,
$$|z^w|=|z|^w.$$
add a comment |
up vote
0
down vote
$$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$
But notice that the argument is not uniquely defined, you need to choose a branch.
Obviously, for real $w$,
$$|z^w|=|z|^w.$$
add a comment |
up vote
0
down vote
up vote
0
down vote
$$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$
But notice that the argument is not uniquely defined, you need to choose a branch.
Obviously, for real $w$,
$$|z^w|=|z|^w.$$
$$left|z^wright|=left|e^{wlog z}right|=e^{Re(wlog z)}=e^{Re(w)log|z|-Im(w)arg(z)}=|z|^{Re(w)}e^{-Im(w)arg(z)}.$$
But notice that the argument is not uniquely defined, you need to choose a branch.
Obviously, for real $w$,
$$|z^w|=|z|^w.$$
edited Nov 16 at 17:36
answered Nov 16 at 17:30
Yves Daoust
121k668216
121k668216
add a comment |
add a comment |
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Writing $z$ in polar form might be helpful
– Aditya Dua
Nov 16 at 8:47
One could write $z^w = |z|(cos(Arg(z))+isin(Arg(z)))^{|w|(cos(Arg(w))+isin(Arg(w)))} = left(|z|e^{Arg(z)i}right)^{|w|e^{Arg(w)i}} = |z|e^{Arg(z)|w|e^{Arg(w)i}i}$, but I dont know if that will make the proportionality any more obvious..
– Nils Phillip Talgö
Nov 16 at 9:52