Writing the proof for the maximum norm

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I am looking to prove that $|v | _infty = max_i |v_i|$ and show that it satisfies the norm conditions of:



  1. positivity

  2. scalar quantity

  3. triangle inequality

So far I know that:
$$| v |_infty = max _i | v_i |$$



Where $ v= (v_1, v_2, v_3, ldots v_n )$ and $n| v |_infty = nmax _i | v_i | = sum_i=1^n max_i |v_i|$



Then we say:



$$sum_i=1^n |v_i| leq sum_i=1^nmax _i |v_i| $$



Finally:
$$|v|_1 leq n|v|_infty $$



But, how can I confirm that the conditions are met?










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  • 1




    If by positivity you mean norm nonnegative and 0 only when v=0, that is since norm is a max of nonnegative (because absolute values used), and only way to get 0 is all absolute values of coords are 0, in turn makes all coords zero.It's a scalar quantity since it's a number. Maybe yoou mean norm of kv is |k| times norm of v. The triangle inequality seems it wouldn't be hard, maybe try it first for only a few components of v and see what's going on.
    – coffeemath
    Sep 10 at 7:14















up vote
-1
down vote

favorite
1












I am looking to prove that $|v | _infty = max_i |v_i|$ and show that it satisfies the norm conditions of:



  1. positivity

  2. scalar quantity

  3. triangle inequality

So far I know that:
$$| v |_infty = max _i | v_i |$$



Where $ v= (v_1, v_2, v_3, ldots v_n )$ and $n| v |_infty = nmax _i | v_i | = sum_i=1^n max_i |v_i|$



Then we say:



$$sum_i=1^n |v_i| leq sum_i=1^nmax _i |v_i| $$



Finally:
$$|v|_1 leq n|v|_infty $$



But, how can I confirm that the conditions are met?










share|cite|improve this question



















  • 1




    If by positivity you mean norm nonnegative and 0 only when v=0, that is since norm is a max of nonnegative (because absolute values used), and only way to get 0 is all absolute values of coords are 0, in turn makes all coords zero.It's a scalar quantity since it's a number. Maybe yoou mean norm of kv is |k| times norm of v. The triangle inequality seems it wouldn't be hard, maybe try it first for only a few components of v and see what's going on.
    – coffeemath
    Sep 10 at 7:14













up vote
-1
down vote

favorite
1









up vote
-1
down vote

favorite
1






1





I am looking to prove that $|v | _infty = max_i |v_i|$ and show that it satisfies the norm conditions of:



  1. positivity

  2. scalar quantity

  3. triangle inequality

So far I know that:
$$| v |_infty = max _i | v_i |$$



Where $ v= (v_1, v_2, v_3, ldots v_n )$ and $n| v |_infty = nmax _i | v_i | = sum_i=1^n max_i |v_i|$



Then we say:



$$sum_i=1^n |v_i| leq sum_i=1^nmax _i |v_i| $$



Finally:
$$|v|_1 leq n|v|_infty $$



But, how can I confirm that the conditions are met?










share|cite|improve this question















I am looking to prove that $|v | _infty = max_i |v_i|$ and show that it satisfies the norm conditions of:



  1. positivity

  2. scalar quantity

  3. triangle inequality

So far I know that:
$$| v |_infty = max _i | v_i |$$



Where $ v= (v_1, v_2, v_3, ldots v_n )$ and $n| v |_infty = nmax _i | v_i | = sum_i=1^n max_i |v_i|$



Then we say:



$$sum_i=1^n |v_i| leq sum_i=1^nmax _i |v_i| $$



Finally:
$$|v|_1 leq n|v|_infty $$



But, how can I confirm that the conditions are met?







matrices proof-verification norm






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edited Sep 10 at 7:23









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asked Sep 10 at 6:59









frobeniusabnorms90776

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  • 1




    If by positivity you mean norm nonnegative and 0 only when v=0, that is since norm is a max of nonnegative (because absolute values used), and only way to get 0 is all absolute values of coords are 0, in turn makes all coords zero.It's a scalar quantity since it's a number. Maybe yoou mean norm of kv is |k| times norm of v. The triangle inequality seems it wouldn't be hard, maybe try it first for only a few components of v and see what's going on.
    – coffeemath
    Sep 10 at 7:14













  • 1




    If by positivity you mean norm nonnegative and 0 only when v=0, that is since norm is a max of nonnegative (because absolute values used), and only way to get 0 is all absolute values of coords are 0, in turn makes all coords zero.It's a scalar quantity since it's a number. Maybe yoou mean norm of kv is |k| times norm of v. The triangle inequality seems it wouldn't be hard, maybe try it first for only a few components of v and see what's going on.
    – coffeemath
    Sep 10 at 7:14








1




1




If by positivity you mean norm nonnegative and 0 only when v=0, that is since norm is a max of nonnegative (because absolute values used), and only way to get 0 is all absolute values of coords are 0, in turn makes all coords zero.It's a scalar quantity since it's a number. Maybe yoou mean norm of kv is |k| times norm of v. The triangle inequality seems it wouldn't be hard, maybe try it first for only a few components of v and see what's going on.
– coffeemath
Sep 10 at 7:14





If by positivity you mean norm nonnegative and 0 only when v=0, that is since norm is a max of nonnegative (because absolute values used), and only way to get 0 is all absolute values of coords are 0, in turn makes all coords zero.It's a scalar quantity since it's a number. Maybe yoou mean norm of kv is |k| times norm of v. The triangle inequality seems it wouldn't be hard, maybe try it first for only a few components of v and see what's going on.
– coffeemath
Sep 10 at 7:14
















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