How to find all the $z$ that satisfy $(1+i)z^4=(1-i)|z|^2$?
Clash Royale CLAN TAG#URR8PPP
up vote
3
down vote
favorite
Would you please help me solve this? I need all the $z$ that satisfy the equality
$$(1+i)z^4=(1-i)|z|^2.$$
I tried doing this:
$$
beginaligned
(1+i)z^4&= (1-i)zoverline z\
(1+i)z^4 -(1-i)zoverline z &= 0\
z[(1+i)z^3-(1-i)overline z]&= 0
endaligned
$$
Then $z= 0$ and
$$(1+i)z^3-(1-i)overline z= 0.$$
I don't know what to do with $overline z$.
calculus complex-analysis complex-numbers
add a comment |Â
up vote
3
down vote
favorite
Would you please help me solve this? I need all the $z$ that satisfy the equality
$$(1+i)z^4=(1-i)|z|^2.$$
I tried doing this:
$$
beginaligned
(1+i)z^4&= (1-i)zoverline z\
(1+i)z^4 -(1-i)zoverline z &= 0\
z[(1+i)z^3-(1-i)overline z]&= 0
endaligned
$$
Then $z= 0$ and
$$(1+i)z^3-(1-i)overline z= 0.$$
I don't know what to do with $overline z$.
calculus complex-analysis complex-numbers
2
Consider the absolute value of both sides, then you can easily see that $z$ must be uni-modular or zero. That is $|z|=0, 1.$ Than take $z=costheta+isintheta$ and substitute to your equation to find particular conditions on $theta.$
â Bumblebee
Aug 20 at 0:57
add a comment |Â
up vote
3
down vote
favorite
up vote
3
down vote
favorite
Would you please help me solve this? I need all the $z$ that satisfy the equality
$$(1+i)z^4=(1-i)|z|^2.$$
I tried doing this:
$$
beginaligned
(1+i)z^4&= (1-i)zoverline z\
(1+i)z^4 -(1-i)zoverline z &= 0\
z[(1+i)z^3-(1-i)overline z]&= 0
endaligned
$$
Then $z= 0$ and
$$(1+i)z^3-(1-i)overline z= 0.$$
I don't know what to do with $overline z$.
calculus complex-analysis complex-numbers
Would you please help me solve this? I need all the $z$ that satisfy the equality
$$(1+i)z^4=(1-i)|z|^2.$$
I tried doing this:
$$
beginaligned
(1+i)z^4&= (1-i)zoverline z\
(1+i)z^4 -(1-i)zoverline z &= 0\
z[(1+i)z^3-(1-i)overline z]&= 0
endaligned
$$
Then $z= 0$ and
$$(1+i)z^3-(1-i)overline z= 0.$$
I don't know what to do with $overline z$.
calculus complex-analysis complex-numbers
calculus complex-analysis complex-numbers
edited Aug 20 at 3:26
AccidentalFourierTransform
1,335627
1,335627
asked Aug 19 at 23:06
tina_98
636
636
2
Consider the absolute value of both sides, then you can easily see that $z$ must be uni-modular or zero. That is $|z|=0, 1.$ Than take $z=costheta+isintheta$ and substitute to your equation to find particular conditions on $theta.$
â Bumblebee
Aug 20 at 0:57
add a comment |Â
2
Consider the absolute value of both sides, then you can easily see that $z$ must be uni-modular or zero. That is $|z|=0, 1.$ Than take $z=costheta+isintheta$ and substitute to your equation to find particular conditions on $theta.$
â Bumblebee
Aug 20 at 0:57
2
2
Consider the absolute value of both sides, then you can easily see that $z$ must be uni-modular or zero. That is $|z|=0, 1.$ Than take $z=costheta+isintheta$ and substitute to your equation to find particular conditions on $theta.$
â Bumblebee
Aug 20 at 0:57
Consider the absolute value of both sides, then you can easily see that $z$ must be uni-modular or zero. That is $|z|=0, 1.$ Than take $z=costheta+isintheta$ and substitute to your equation to find particular conditions on $theta.$
â Bumblebee
Aug 20 at 0:57
add a comment |Â
2 Answers
2
active
oldest
votes
up vote
6
down vote
Hint
$$(1+i)z^4=(1-i)|z|^2iff z^4=dfrac1-i1+i|z|^2=-i|z|^2.$$
Taking modulus we have $|z|=0$ or $|z|=1.$ In the first case it is $z=0.$ In the second case $z=e^itheta.$ So, we have
$$cos (4theta)+isin(4theta)=-i.$$ That is, we have to solve
begincasescos(4theta)=0\sin(4theta)=-1endcases
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
1
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
add a comment |Â
up vote
0
down vote
$$(1+i)z^4=(1-i)|z|^2iff iz^4=zbar ziffbegincasesz=0\iz^3=bar zendcases$$ $$iz^3=bar ziff i(a+ib)^3=(a-ib)iff ia^3 - 3 a^2 b -i 3 a b^2 + b^3=(a-ib)\iff b^3- 3 a^2 b +i(a^3 - 3 a b^2)=a-ibiffbegincasesb^3- 3 a^2 b=a\a^3 - 3 a b^2=-bendcases$$
We can also notice that $|b^3- 3 a^2 b +i(a^3 - 3 a b^2)|=sqrt(a^2+b^2)^3=sqrta^2+b^2=|a-ib|implies
|z|=begincases1\0endcases$, so it comes with terms with @mfl's answer
1
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
add a comment |Â
2 Answers
2
active
oldest
votes
2 Answers
2
active
oldest
votes
active
oldest
votes
active
oldest
votes
up vote
6
down vote
Hint
$$(1+i)z^4=(1-i)|z|^2iff z^4=dfrac1-i1+i|z|^2=-i|z|^2.$$
Taking modulus we have $|z|=0$ or $|z|=1.$ In the first case it is $z=0.$ In the second case $z=e^itheta.$ So, we have
$$cos (4theta)+isin(4theta)=-i.$$ That is, we have to solve
begincasescos(4theta)=0\sin(4theta)=-1endcases
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
1
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
add a comment |Â
up vote
6
down vote
Hint
$$(1+i)z^4=(1-i)|z|^2iff z^4=dfrac1-i1+i|z|^2=-i|z|^2.$$
Taking modulus we have $|z|=0$ or $|z|=1.$ In the first case it is $z=0.$ In the second case $z=e^itheta.$ So, we have
$$cos (4theta)+isin(4theta)=-i.$$ That is, we have to solve
begincasescos(4theta)=0\sin(4theta)=-1endcases
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
1
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
add a comment |Â
up vote
6
down vote
up vote
6
down vote
Hint
$$(1+i)z^4=(1-i)|z|^2iff z^4=dfrac1-i1+i|z|^2=-i|z|^2.$$
Taking modulus we have $|z|=0$ or $|z|=1.$ In the first case it is $z=0.$ In the second case $z=e^itheta.$ So, we have
$$cos (4theta)+isin(4theta)=-i.$$ That is, we have to solve
begincasescos(4theta)=0\sin(4theta)=-1endcases
Hint
$$(1+i)z^4=(1-i)|z|^2iff z^4=dfrac1-i1+i|z|^2=-i|z|^2.$$
Taking modulus we have $|z|=0$ or $|z|=1.$ In the first case it is $z=0.$ In the second case $z=e^itheta.$ So, we have
$$cos (4theta)+isin(4theta)=-i.$$ That is, we have to solve
begincasescos(4theta)=0\sin(4theta)=-1endcases
edited Aug 19 at 23:32
answered Aug 19 at 23:16
mfl
25.2k12141
25.2k12141
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
1
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
add a comment |Â
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
1
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
I dont understand why you consider the modulus as 0 and 1
â tina_98
Aug 19 at 23:34
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
$z^4=-i|z|^2implies |z|^4=|z^4|=|-i|z|^2|=|-i||z|^2=|z|^2implies |z|^4=|z|^2.$
â mfl
Aug 19 at 23:35
1
1
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
There is an easier way to solve $e^4itheta=-i$. Just use $e^4itheta=e^3pi i/2+2kpi i$, or $4itheta=3pi/2 i+2kpi i$.
â Rory Daulton
Aug 20 at 0:16
add a comment |Â
up vote
0
down vote
$$(1+i)z^4=(1-i)|z|^2iff iz^4=zbar ziffbegincasesz=0\iz^3=bar zendcases$$ $$iz^3=bar ziff i(a+ib)^3=(a-ib)iff ia^3 - 3 a^2 b -i 3 a b^2 + b^3=(a-ib)\iff b^3- 3 a^2 b +i(a^3 - 3 a b^2)=a-ibiffbegincasesb^3- 3 a^2 b=a\a^3 - 3 a b^2=-bendcases$$
We can also notice that $|b^3- 3 a^2 b +i(a^3 - 3 a b^2)|=sqrt(a^2+b^2)^3=sqrta^2+b^2=|a-ib|implies
|z|=begincases1\0endcases$, so it comes with terms with @mfl's answer
1
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
add a comment |Â
up vote
0
down vote
$$(1+i)z^4=(1-i)|z|^2iff iz^4=zbar ziffbegincasesz=0\iz^3=bar zendcases$$ $$iz^3=bar ziff i(a+ib)^3=(a-ib)iff ia^3 - 3 a^2 b -i 3 a b^2 + b^3=(a-ib)\iff b^3- 3 a^2 b +i(a^3 - 3 a b^2)=a-ibiffbegincasesb^3- 3 a^2 b=a\a^3 - 3 a b^2=-bendcases$$
We can also notice that $|b^3- 3 a^2 b +i(a^3 - 3 a b^2)|=sqrt(a^2+b^2)^3=sqrta^2+b^2=|a-ib|implies
|z|=begincases1\0endcases$, so it comes with terms with @mfl's answer
1
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
add a comment |Â
up vote
0
down vote
up vote
0
down vote
$$(1+i)z^4=(1-i)|z|^2iff iz^4=zbar ziffbegincasesz=0\iz^3=bar zendcases$$ $$iz^3=bar ziff i(a+ib)^3=(a-ib)iff ia^3 - 3 a^2 b -i 3 a b^2 + b^3=(a-ib)\iff b^3- 3 a^2 b +i(a^3 - 3 a b^2)=a-ibiffbegincasesb^3- 3 a^2 b=a\a^3 - 3 a b^2=-bendcases$$
We can also notice that $|b^3- 3 a^2 b +i(a^3 - 3 a b^2)|=sqrt(a^2+b^2)^3=sqrta^2+b^2=|a-ib|implies
|z|=begincases1\0endcases$, so it comes with terms with @mfl's answer
$$(1+i)z^4=(1-i)|z|^2iff iz^4=zbar ziffbegincasesz=0\iz^3=bar zendcases$$ $$iz^3=bar ziff i(a+ib)^3=(a-ib)iff ia^3 - 3 a^2 b -i 3 a b^2 + b^3=(a-ib)\iff b^3- 3 a^2 b +i(a^3 - 3 a b^2)=a-ibiffbegincasesb^3- 3 a^2 b=a\a^3 - 3 a b^2=-bendcases$$
We can also notice that $|b^3- 3 a^2 b +i(a^3 - 3 a b^2)|=sqrt(a^2+b^2)^3=sqrta^2+b^2=|a-ib|implies
|z|=begincases1\0endcases$, so it comes with terms with @mfl's answer
answered Aug 20 at 0:17
Holo
4,7472729
4,7472729
1
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
add a comment |Â
1
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
1
1
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
No idea why you send the OP to the real part / imaginary part decomposition when it only complicates things. How would you solve $iz^9=bar z$, one wonders...
â Did
Aug 20 at 18:41
add a comment |Â
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
StackExchange.ready(
function ()
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fmath.stackexchange.com%2fquestions%2f2888218%2fhow-to-find-all-the-z-that-satisfy-1iz4-1-iz2%23new-answer', 'question_page');
);
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Post as a guest
Sign up or log in
StackExchange.ready(function ()
StackExchange.helpers.onClickDraftSave('#login-link');
);
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
Sign up using Google
Sign up using Facebook
Sign up using Email and Password
2
Consider the absolute value of both sides, then you can easily see that $z$ must be uni-modular or zero. That is $|z|=0, 1.$ Than take $z=costheta+isintheta$ and substitute to your equation to find particular conditions on $theta.$
â Bumblebee
Aug 20 at 0:57