Can we write complex functions in polar form? Consider the cases $mathbb Rto mathbb C$ and $mathbb Cto mathbb...











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For a complex number $zin mathbb C$, we can write $z=a+ib=sqrt{a^2+b^2}, e^{iphi}$, where $phi=arctanfrac{b}{a}$ and $a,b,thetain mathbb R$ .



Is this also true for complex functions?



I'm interested in two cases.



Case 1:



Let $f:mathbb Rtomathbb C$ and $u,v:mathbb Rto mathbb R$.



Can we write



$$f(t)=u(t)+iv(t)=sqrt{u(t)^2+v(t)^2}, e^{itheta (t)},$$
where $theta:mathbb Rto mathbb R$, so $theta (t)=arctan{frac{v(t)}{u(t)}}$ ?



Case 2:



Let $f:mathbb Ctomathbb C$ and $u,v:mathbb R^2to mathbb R$.



Can we write



begin{align}
f(z)&=f(x+iy)=u(x,y)+iv(x,y)\
&=sqrt{u(x,y)^2+v(x,y)^2}, e^{itheta (x,y)},
end{align}

where $theta:mathbb R^2to mathbb R$, so $theta (x,y)=arctan{frac{v(x,y)}{u(x,y)}}$ ?



Are these cases correct?










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  • $arctanfrac{v(t)}{u(t)}$ might not be defined, $u$ might have zeros, the definition of $theta$ is not that lucky, better use the argument function.
    – Peter Melech
    Nov 14 at 11:16















up vote
0
down vote

favorite
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For a complex number $zin mathbb C$, we can write $z=a+ib=sqrt{a^2+b^2}, e^{iphi}$, where $phi=arctanfrac{b}{a}$ and $a,b,thetain mathbb R$ .



Is this also true for complex functions?



I'm interested in two cases.



Case 1:



Let $f:mathbb Rtomathbb C$ and $u,v:mathbb Rto mathbb R$.



Can we write



$$f(t)=u(t)+iv(t)=sqrt{u(t)^2+v(t)^2}, e^{itheta (t)},$$
where $theta:mathbb Rto mathbb R$, so $theta (t)=arctan{frac{v(t)}{u(t)}}$ ?



Case 2:



Let $f:mathbb Ctomathbb C$ and $u,v:mathbb R^2to mathbb R$.



Can we write



begin{align}
f(z)&=f(x+iy)=u(x,y)+iv(x,y)\
&=sqrt{u(x,y)^2+v(x,y)^2}, e^{itheta (x,y)},
end{align}

where $theta:mathbb R^2to mathbb R$, so $theta (x,y)=arctan{frac{v(x,y)}{u(x,y)}}$ ?



Are these cases correct?










share|cite|improve this question
























  • $arctanfrac{v(t)}{u(t)}$ might not be defined, $u$ might have zeros, the definition of $theta$ is not that lucky, better use the argument function.
    – Peter Melech
    Nov 14 at 11:16













up vote
0
down vote

favorite
1









up vote
0
down vote

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For a complex number $zin mathbb C$, we can write $z=a+ib=sqrt{a^2+b^2}, e^{iphi}$, where $phi=arctanfrac{b}{a}$ and $a,b,thetain mathbb R$ .



Is this also true for complex functions?



I'm interested in two cases.



Case 1:



Let $f:mathbb Rtomathbb C$ and $u,v:mathbb Rto mathbb R$.



Can we write



$$f(t)=u(t)+iv(t)=sqrt{u(t)^2+v(t)^2}, e^{itheta (t)},$$
where $theta:mathbb Rto mathbb R$, so $theta (t)=arctan{frac{v(t)}{u(t)}}$ ?



Case 2:



Let $f:mathbb Ctomathbb C$ and $u,v:mathbb R^2to mathbb R$.



Can we write



begin{align}
f(z)&=f(x+iy)=u(x,y)+iv(x,y)\
&=sqrt{u(x,y)^2+v(x,y)^2}, e^{itheta (x,y)},
end{align}

where $theta:mathbb R^2to mathbb R$, so $theta (x,y)=arctan{frac{v(x,y)}{u(x,y)}}$ ?



Are these cases correct?










share|cite|improve this question















For a complex number $zin mathbb C$, we can write $z=a+ib=sqrt{a^2+b^2}, e^{iphi}$, where $phi=arctanfrac{b}{a}$ and $a,b,thetain mathbb R$ .



Is this also true for complex functions?



I'm interested in two cases.



Case 1:



Let $f:mathbb Rtomathbb C$ and $u,v:mathbb Rto mathbb R$.



Can we write



$$f(t)=u(t)+iv(t)=sqrt{u(t)^2+v(t)^2}, e^{itheta (t)},$$
where $theta:mathbb Rto mathbb R$, so $theta (t)=arctan{frac{v(t)}{u(t)}}$ ?



Case 2:



Let $f:mathbb Ctomathbb C$ and $u,v:mathbb R^2to mathbb R$.



Can we write



begin{align}
f(z)&=f(x+iy)=u(x,y)+iv(x,y)\
&=sqrt{u(x,y)^2+v(x,y)^2}, e^{itheta (x,y)},
end{align}

where $theta:mathbb R^2to mathbb R$, so $theta (x,y)=arctan{frac{v(x,y)}{u(x,y)}}$ ?



Are these cases correct?







complex-analysis






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share|cite|improve this question













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edited Nov 14 at 10:39

























asked Nov 14 at 10:23









JDoeDoe

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  • $arctanfrac{v(t)}{u(t)}$ might not be defined, $u$ might have zeros, the definition of $theta$ is not that lucky, better use the argument function.
    – Peter Melech
    Nov 14 at 11:16


















  • $arctanfrac{v(t)}{u(t)}$ might not be defined, $u$ might have zeros, the definition of $theta$ is not that lucky, better use the argument function.
    – Peter Melech
    Nov 14 at 11:16
















$arctanfrac{v(t)}{u(t)}$ might not be defined, $u$ might have zeros, the definition of $theta$ is not that lucky, better use the argument function.
– Peter Melech
Nov 14 at 11:16




$arctanfrac{v(t)}{u(t)}$ might not be defined, $u$ might have zeros, the definition of $theta$ is not that lucky, better use the argument function.
– Peter Melech
Nov 14 at 11:16















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