Dot product with a constant












4












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What is $vec{a}cdot (vec{b}+c)$, where $c$ is a constant?




Am I able to just take out the constant, or do I multiply the constant by the vector as a scalar?










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  • $begingroup$
    This only makes sense if you make a vector space out of the base field
    $endgroup$
    – Brevan Ellefsen
    1 hour ago
















4












$begingroup$



What is $vec{a}cdot (vec{b}+c)$, where $c$ is a constant?




Am I able to just take out the constant, or do I multiply the constant by the vector as a scalar?










share|cite|improve this question









New contributor




ItIsLastThursday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$












  • $begingroup$
    This only makes sense if you make a vector space out of the base field
    $endgroup$
    – Brevan Ellefsen
    1 hour ago














4












4








4





$begingroup$



What is $vec{a}cdot (vec{b}+c)$, where $c$ is a constant?




Am I able to just take out the constant, or do I multiply the constant by the vector as a scalar?










share|cite|improve this question









New contributor




ItIsLastThursday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.







$endgroup$





What is $vec{a}cdot (vec{b}+c)$, where $c$ is a constant?




Am I able to just take out the constant, or do I multiply the constant by the vector as a scalar?







abstract-algebra vectors






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ItIsLastThursday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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ItIsLastThursday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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share|cite|improve this question




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edited 4 hours ago









greedoid

43.5k1154107




43.5k1154107






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asked 4 hours ago









ItIsLastThursdayItIsLastThursday

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212




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ItIsLastThursday is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
Check out our Code of Conduct.






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Check out our Code of Conduct.












  • $begingroup$
    This only makes sense if you make a vector space out of the base field
    $endgroup$
    – Brevan Ellefsen
    1 hour ago


















  • $begingroup$
    This only makes sense if you make a vector space out of the base field
    $endgroup$
    – Brevan Ellefsen
    1 hour ago
















$begingroup$
This only makes sense if you make a vector space out of the base field
$endgroup$
– Brevan Ellefsen
1 hour ago




$begingroup$
This only makes sense if you make a vector space out of the base field
$endgroup$
– Brevan Ellefsen
1 hour ago










2 Answers
2






active

oldest

votes


















15












$begingroup$

This product has no meaning since the sum in the parentheses is undefined; you can not add a vector and a scalar.



$c$ must be a vector, then the sum is defined and the given product is a dot product.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    So is there any answer I can get?
    $endgroup$
    – ItIsLastThursday
    4 hours ago






  • 6




    $begingroup$
    No, if $c$ is a scalar then there is no answer.
    $endgroup$
    – greedoid
    4 hours ago










  • $begingroup$
    You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
    $endgroup$
    – Matt Samuel
    17 mins ago



















4












$begingroup$

For an expression to be defined, all of its constituting parts need to be defined as well.



The sum of a vector and a constant $vec b + c$ is not defined, and hence the expression $vec a cdot (vec b + c)$ is not defined.



This applies to any scalar, not just constants, because $c$ can depend on another variable.





Although it probably makes sense to you that
$$vec a cdot (vec b + c) = vec a cdot vec b + c cdot vec a$$
neither side of the equation is defined, which means that you cannot use distribution the way it was used above.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    The RHS expression isn't defined either.
    $endgroup$
    – Hammerite
    2 hours ago










  • $begingroup$
    @Hammerite You are right. What a silly mistake. Thank you!
    $endgroup$
    – Haris Gusic
    2 hours ago











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2 Answers
2






active

oldest

votes








2 Answers
2






active

oldest

votes









active

oldest

votes






active

oldest

votes









15












$begingroup$

This product has no meaning since the sum in the parentheses is undefined; you can not add a vector and a scalar.



$c$ must be a vector, then the sum is defined and the given product is a dot product.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    So is there any answer I can get?
    $endgroup$
    – ItIsLastThursday
    4 hours ago






  • 6




    $begingroup$
    No, if $c$ is a scalar then there is no answer.
    $endgroup$
    – greedoid
    4 hours ago










  • $begingroup$
    You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
    $endgroup$
    – Matt Samuel
    17 mins ago
















15












$begingroup$

This product has no meaning since the sum in the parentheses is undefined; you can not add a vector and a scalar.



$c$ must be a vector, then the sum is defined and the given product is a dot product.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    So is there any answer I can get?
    $endgroup$
    – ItIsLastThursday
    4 hours ago






  • 6




    $begingroup$
    No, if $c$ is a scalar then there is no answer.
    $endgroup$
    – greedoid
    4 hours ago










  • $begingroup$
    You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
    $endgroup$
    – Matt Samuel
    17 mins ago














15












15








15





$begingroup$

This product has no meaning since the sum in the parentheses is undefined; you can not add a vector and a scalar.



$c$ must be a vector, then the sum is defined and the given product is a dot product.






share|cite|improve this answer











$endgroup$



This product has no meaning since the sum in the parentheses is undefined; you can not add a vector and a scalar.



$c$ must be a vector, then the sum is defined and the given product is a dot product.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited 59 mins ago









Eevee Trainer

6,53811237




6,53811237










answered 4 hours ago









greedoidgreedoid

43.5k1154107




43.5k1154107












  • $begingroup$
    So is there any answer I can get?
    $endgroup$
    – ItIsLastThursday
    4 hours ago






  • 6




    $begingroup$
    No, if $c$ is a scalar then there is no answer.
    $endgroup$
    – greedoid
    4 hours ago










  • $begingroup$
    You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
    $endgroup$
    – Matt Samuel
    17 mins ago


















  • $begingroup$
    So is there any answer I can get?
    $endgroup$
    – ItIsLastThursday
    4 hours ago






  • 6




    $begingroup$
    No, if $c$ is a scalar then there is no answer.
    $endgroup$
    – greedoid
    4 hours ago










  • $begingroup$
    You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
    $endgroup$
    – Matt Samuel
    17 mins ago
















$begingroup$
So is there any answer I can get?
$endgroup$
– ItIsLastThursday
4 hours ago




$begingroup$
So is there any answer I can get?
$endgroup$
– ItIsLastThursday
4 hours ago




6




6




$begingroup$
No, if $c$ is a scalar then there is no answer.
$endgroup$
– greedoid
4 hours ago




$begingroup$
No, if $c$ is a scalar then there is no answer.
$endgroup$
– greedoid
4 hours ago












$begingroup$
You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
$endgroup$
– Matt Samuel
17 mins ago




$begingroup$
You can add a vector and a scalar in a more advanced context. This is like when all of my grade school teachers said you couldn't take the square root of a negative number, and I was ahead so I knew they were lying.
$endgroup$
– Matt Samuel
17 mins ago











4












$begingroup$

For an expression to be defined, all of its constituting parts need to be defined as well.



The sum of a vector and a constant $vec b + c$ is not defined, and hence the expression $vec a cdot (vec b + c)$ is not defined.



This applies to any scalar, not just constants, because $c$ can depend on another variable.





Although it probably makes sense to you that
$$vec a cdot (vec b + c) = vec a cdot vec b + c cdot vec a$$
neither side of the equation is defined, which means that you cannot use distribution the way it was used above.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    The RHS expression isn't defined either.
    $endgroup$
    – Hammerite
    2 hours ago










  • $begingroup$
    @Hammerite You are right. What a silly mistake. Thank you!
    $endgroup$
    – Haris Gusic
    2 hours ago
















4












$begingroup$

For an expression to be defined, all of its constituting parts need to be defined as well.



The sum of a vector and a constant $vec b + c$ is not defined, and hence the expression $vec a cdot (vec b + c)$ is not defined.



This applies to any scalar, not just constants, because $c$ can depend on another variable.





Although it probably makes sense to you that
$$vec a cdot (vec b + c) = vec a cdot vec b + c cdot vec a$$
neither side of the equation is defined, which means that you cannot use distribution the way it was used above.






share|cite|improve this answer











$endgroup$













  • $begingroup$
    The RHS expression isn't defined either.
    $endgroup$
    – Hammerite
    2 hours ago










  • $begingroup$
    @Hammerite You are right. What a silly mistake. Thank you!
    $endgroup$
    – Haris Gusic
    2 hours ago














4












4








4





$begingroup$

For an expression to be defined, all of its constituting parts need to be defined as well.



The sum of a vector and a constant $vec b + c$ is not defined, and hence the expression $vec a cdot (vec b + c)$ is not defined.



This applies to any scalar, not just constants, because $c$ can depend on another variable.





Although it probably makes sense to you that
$$vec a cdot (vec b + c) = vec a cdot vec b + c cdot vec a$$
neither side of the equation is defined, which means that you cannot use distribution the way it was used above.






share|cite|improve this answer











$endgroup$



For an expression to be defined, all of its constituting parts need to be defined as well.



The sum of a vector and a constant $vec b + c$ is not defined, and hence the expression $vec a cdot (vec b + c)$ is not defined.



This applies to any scalar, not just constants, because $c$ can depend on another variable.





Although it probably makes sense to you that
$$vec a cdot (vec b + c) = vec a cdot vec b + c cdot vec a$$
neither side of the equation is defined, which means that you cannot use distribution the way it was used above.







share|cite|improve this answer














share|cite|improve this answer



share|cite|improve this answer








edited 1 hour ago

























answered 4 hours ago









Haris GusicHaris Gusic

1,142116




1,142116












  • $begingroup$
    The RHS expression isn't defined either.
    $endgroup$
    – Hammerite
    2 hours ago










  • $begingroup$
    @Hammerite You are right. What a silly mistake. Thank you!
    $endgroup$
    – Haris Gusic
    2 hours ago


















  • $begingroup$
    The RHS expression isn't defined either.
    $endgroup$
    – Hammerite
    2 hours ago










  • $begingroup$
    @Hammerite You are right. What a silly mistake. Thank you!
    $endgroup$
    – Haris Gusic
    2 hours ago
















$begingroup$
The RHS expression isn't defined either.
$endgroup$
– Hammerite
2 hours ago




$begingroup$
The RHS expression isn't defined either.
$endgroup$
– Hammerite
2 hours ago












$begingroup$
@Hammerite You are right. What a silly mistake. Thank you!
$endgroup$
– Haris Gusic
2 hours ago




$begingroup$
@Hammerite You are right. What a silly mistake. Thank you!
$endgroup$
– Haris Gusic
2 hours ago










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