Intersection of two subgroups

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Let $G$ be a group and $H$, $K$ two cyclic subgroups of $G$ of the same order such that:$$
H=langle xrangle,~~K=langle yrangle~~ textand~~xneq y.$$
Can we said that $Hcap K$ is trivial?
Thank you







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  • In fact, it's false.
    – Rafael Gonzalez Lopez
    Aug 7 at 17:44










  • You can't even say that $H$ and $K$ are either equal or have trivial intersection: In $mathbb Z_p^2timesmathbb Z_p$ consider $langle (1,0)rangle$ versus $langle(1,1)rangle$.
    – Henning Makholm
    Aug 7 at 17:54










  • Of course you can say it if you want to, but it would be false.
    – Derek Holt
    Aug 7 at 19:29










  • Since you are new to here, just as a reminder for you: After you read the answers given, if there exists an answer that you accept it, click the tick beside the answer. If there does not exist, comment below the answer to state that which part of the answer you need more elaboration.
    – Alan Wang
    Aug 8 at 13:58














up vote
2
down vote

favorite












Let $G$ be a group and $H$, $K$ two cyclic subgroups of $G$ of the same order such that:$$
H=langle xrangle,~~K=langle yrangle~~ textand~~xneq y.$$
Can we said that $Hcap K$ is trivial?
Thank you







share|cite|improve this question






















  • In fact, it's false.
    – Rafael Gonzalez Lopez
    Aug 7 at 17:44










  • You can't even say that $H$ and $K$ are either equal or have trivial intersection: In $mathbb Z_p^2timesmathbb Z_p$ consider $langle (1,0)rangle$ versus $langle(1,1)rangle$.
    – Henning Makholm
    Aug 7 at 17:54










  • Of course you can say it if you want to, but it would be false.
    – Derek Holt
    Aug 7 at 19:29










  • Since you are new to here, just as a reminder for you: After you read the answers given, if there exists an answer that you accept it, click the tick beside the answer. If there does not exist, comment below the answer to state that which part of the answer you need more elaboration.
    – Alan Wang
    Aug 8 at 13:58












up vote
2
down vote

favorite









up vote
2
down vote

favorite











Let $G$ be a group and $H$, $K$ two cyclic subgroups of $G$ of the same order such that:$$
H=langle xrangle,~~K=langle yrangle~~ textand~~xneq y.$$
Can we said that $Hcap K$ is trivial?
Thank you







share|cite|improve this question














Let $G$ be a group and $H$, $K$ two cyclic subgroups of $G$ of the same order such that:$$
H=langle xrangle,~~K=langle yrangle~~ textand~~xneq y.$$
Can we said that $Hcap K$ is trivial?
Thank you









share|cite|improve this question













share|cite|improve this question




share|cite|improve this question








edited Aug 7 at 17:47









Arnaud Mortier

19.6k22159




19.6k22159










asked Aug 7 at 17:40









Amine El Bouzidi

344




344











  • In fact, it's false.
    – Rafael Gonzalez Lopez
    Aug 7 at 17:44










  • You can't even say that $H$ and $K$ are either equal or have trivial intersection: In $mathbb Z_p^2timesmathbb Z_p$ consider $langle (1,0)rangle$ versus $langle(1,1)rangle$.
    – Henning Makholm
    Aug 7 at 17:54










  • Of course you can say it if you want to, but it would be false.
    – Derek Holt
    Aug 7 at 19:29










  • Since you are new to here, just as a reminder for you: After you read the answers given, if there exists an answer that you accept it, click the tick beside the answer. If there does not exist, comment below the answer to state that which part of the answer you need more elaboration.
    – Alan Wang
    Aug 8 at 13:58
















  • In fact, it's false.
    – Rafael Gonzalez Lopez
    Aug 7 at 17:44










  • You can't even say that $H$ and $K$ are either equal or have trivial intersection: In $mathbb Z_p^2timesmathbb Z_p$ consider $langle (1,0)rangle$ versus $langle(1,1)rangle$.
    – Henning Makholm
    Aug 7 at 17:54










  • Of course you can say it if you want to, but it would be false.
    – Derek Holt
    Aug 7 at 19:29










  • Since you are new to here, just as a reminder for you: After you read the answers given, if there exists an answer that you accept it, click the tick beside the answer. If there does not exist, comment below the answer to state that which part of the answer you need more elaboration.
    – Alan Wang
    Aug 8 at 13:58















In fact, it's false.
– Rafael Gonzalez Lopez
Aug 7 at 17:44




In fact, it's false.
– Rafael Gonzalez Lopez
Aug 7 at 17:44












You can't even say that $H$ and $K$ are either equal or have trivial intersection: In $mathbb Z_p^2timesmathbb Z_p$ consider $langle (1,0)rangle$ versus $langle(1,1)rangle$.
– Henning Makholm
Aug 7 at 17:54




You can't even say that $H$ and $K$ are either equal or have trivial intersection: In $mathbb Z_p^2timesmathbb Z_p$ consider $langle (1,0)rangle$ versus $langle(1,1)rangle$.
– Henning Makholm
Aug 7 at 17:54












Of course you can say it if you want to, but it would be false.
– Derek Holt
Aug 7 at 19:29




Of course you can say it if you want to, but it would be false.
– Derek Holt
Aug 7 at 19:29












Since you are new to here, just as a reminder for you: After you read the answers given, if there exists an answer that you accept it, click the tick beside the answer. If there does not exist, comment below the answer to state that which part of the answer you need more elaboration.
– Alan Wang
Aug 8 at 13:58




Since you are new to here, just as a reminder for you: After you read the answers given, if there exists an answer that you accept it, click the tick beside the answer. If there does not exist, comment below the answer to state that which part of the answer you need more elaboration.
– Alan Wang
Aug 8 at 13:58










3 Answers
3






active

oldest

votes

















up vote
5
down vote













No we can't: consider $langle 1rangle=langle 2rangle$ in $Bbb Z/3Bbb Z$.






share|cite|improve this answer




















  • Thank you Arnaud for your answer.
    – Amine El Bouzidi
    Aug 9 at 12:24

















up vote
1
down vote













No, let $H=langle 2 rangle$ and $K=langle 3 rangle$ as subgroups of $mathbbZ$. Then $H cap K = langle 6 rangle $.






share|cite|improve this answer




















  • Thank you Nicky for your answer
    – Amine El Bouzidi
    Aug 9 at 12:24










  • No problem Amine, hope you learned something from all the answers.
    – Nicky Hekster
    Aug 9 at 12:59

















up vote
1
down vote













Another example:



$langle 1 rangle=langle -1 rangle$ in $BbbZ$. So clearly $1neq -1$ but $langle 1 ranglecaplangle -1 rangleneq e$.



By the way, $H$ and $K$ have trivial intersection if $|H|$ and $|K|$ are coprime. This can be proven using Lagrange's Theorem.






share|cite|improve this answer




















  • thank you Alan for your answer
    – Amine El Bouzidi
    Aug 9 at 12:23










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3 Answers
3






active

oldest

votes








3 Answers
3






active

oldest

votes









active

oldest

votes






active

oldest

votes








up vote
5
down vote













No we can't: consider $langle 1rangle=langle 2rangle$ in $Bbb Z/3Bbb Z$.






share|cite|improve this answer




















  • Thank you Arnaud for your answer.
    – Amine El Bouzidi
    Aug 9 at 12:24














up vote
5
down vote













No we can't: consider $langle 1rangle=langle 2rangle$ in $Bbb Z/3Bbb Z$.






share|cite|improve this answer




















  • Thank you Arnaud for your answer.
    – Amine El Bouzidi
    Aug 9 at 12:24












up vote
5
down vote










up vote
5
down vote









No we can't: consider $langle 1rangle=langle 2rangle$ in $Bbb Z/3Bbb Z$.






share|cite|improve this answer












No we can't: consider $langle 1rangle=langle 2rangle$ in $Bbb Z/3Bbb Z$.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Aug 7 at 17:46









Arnaud Mortier

19.6k22159




19.6k22159











  • Thank you Arnaud for your answer.
    – Amine El Bouzidi
    Aug 9 at 12:24
















  • Thank you Arnaud for your answer.
    – Amine El Bouzidi
    Aug 9 at 12:24















Thank you Arnaud for your answer.
– Amine El Bouzidi
Aug 9 at 12:24




Thank you Arnaud for your answer.
– Amine El Bouzidi
Aug 9 at 12:24










up vote
1
down vote













No, let $H=langle 2 rangle$ and $K=langle 3 rangle$ as subgroups of $mathbbZ$. Then $H cap K = langle 6 rangle $.






share|cite|improve this answer




















  • Thank you Nicky for your answer
    – Amine El Bouzidi
    Aug 9 at 12:24










  • No problem Amine, hope you learned something from all the answers.
    – Nicky Hekster
    Aug 9 at 12:59














up vote
1
down vote













No, let $H=langle 2 rangle$ and $K=langle 3 rangle$ as subgroups of $mathbbZ$. Then $H cap K = langle 6 rangle $.






share|cite|improve this answer




















  • Thank you Nicky for your answer
    – Amine El Bouzidi
    Aug 9 at 12:24










  • No problem Amine, hope you learned something from all the answers.
    – Nicky Hekster
    Aug 9 at 12:59












up vote
1
down vote










up vote
1
down vote









No, let $H=langle 2 rangle$ and $K=langle 3 rangle$ as subgroups of $mathbbZ$. Then $H cap K = langle 6 rangle $.






share|cite|improve this answer












No, let $H=langle 2 rangle$ and $K=langle 3 rangle$ as subgroups of $mathbbZ$. Then $H cap K = langle 6 rangle $.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Aug 7 at 18:29









Nicky Hekster

27.1k53152




27.1k53152











  • Thank you Nicky for your answer
    – Amine El Bouzidi
    Aug 9 at 12:24










  • No problem Amine, hope you learned something from all the answers.
    – Nicky Hekster
    Aug 9 at 12:59
















  • Thank you Nicky for your answer
    – Amine El Bouzidi
    Aug 9 at 12:24










  • No problem Amine, hope you learned something from all the answers.
    – Nicky Hekster
    Aug 9 at 12:59















Thank you Nicky for your answer
– Amine El Bouzidi
Aug 9 at 12:24




Thank you Nicky for your answer
– Amine El Bouzidi
Aug 9 at 12:24












No problem Amine, hope you learned something from all the answers.
– Nicky Hekster
Aug 9 at 12:59




No problem Amine, hope you learned something from all the answers.
– Nicky Hekster
Aug 9 at 12:59










up vote
1
down vote













Another example:



$langle 1 rangle=langle -1 rangle$ in $BbbZ$. So clearly $1neq -1$ but $langle 1 ranglecaplangle -1 rangleneq e$.



By the way, $H$ and $K$ have trivial intersection if $|H|$ and $|K|$ are coprime. This can be proven using Lagrange's Theorem.






share|cite|improve this answer




















  • thank you Alan for your answer
    – Amine El Bouzidi
    Aug 9 at 12:23














up vote
1
down vote













Another example:



$langle 1 rangle=langle -1 rangle$ in $BbbZ$. So clearly $1neq -1$ but $langle 1 ranglecaplangle -1 rangleneq e$.



By the way, $H$ and $K$ have trivial intersection if $|H|$ and $|K|$ are coprime. This can be proven using Lagrange's Theorem.






share|cite|improve this answer




















  • thank you Alan for your answer
    – Amine El Bouzidi
    Aug 9 at 12:23












up vote
1
down vote










up vote
1
down vote









Another example:



$langle 1 rangle=langle -1 rangle$ in $BbbZ$. So clearly $1neq -1$ but $langle 1 ranglecaplangle -1 rangleneq e$.



By the way, $H$ and $K$ have trivial intersection if $|H|$ and $|K|$ are coprime. This can be proven using Lagrange's Theorem.






share|cite|improve this answer












Another example:



$langle 1 rangle=langle -1 rangle$ in $BbbZ$. So clearly $1neq -1$ but $langle 1 ranglecaplangle -1 rangleneq e$.



By the way, $H$ and $K$ have trivial intersection if $|H|$ and $|K|$ are coprime. This can be proven using Lagrange's Theorem.







share|cite|improve this answer












share|cite|improve this answer



share|cite|improve this answer










answered Aug 8 at 0:50









Alan Wang

4,559932




4,559932











  • thank you Alan for your answer
    – Amine El Bouzidi
    Aug 9 at 12:23
















  • thank you Alan for your answer
    – Amine El Bouzidi
    Aug 9 at 12:23















thank you Alan for your answer
– Amine El Bouzidi
Aug 9 at 12:23




thank you Alan for your answer
– Amine El Bouzidi
Aug 9 at 12:23

















 

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