Subspace & Span in Rn: Definition & Examples

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The span of a set of vectors in Rn is indeed a subspace, and it can be equal to all of Rn, which is also a subspace of itself. A vector space satisfies the properties of a subspace, including closure under addition and scalar multiplication, as well as containing the zero vector. The example provided illustrates that the span of two vectors in R2 is a subspace, but it does not imply that it is a subspace of Rn where n is greater than 2. Therefore, while all of Rn can be considered a subspace, the span of a specific set of vectors is confined to the dimensions defined by those vectors. Understanding these definitions clarifies the relationship between spans and subspaces.
nobahar
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Hello!
Just a quick question. Is the following okay?:
The span of a set of vectors corresponds to a subspace in Rn.
But the span of a set of vectors can also be ALL of Rn, does that mean all of Rn can be considered a subspace? Or does it mean the first definiton is not entirely correct, and instead a span of a set of vectors can simply be used to identify a subspace, if it exists.
I realize this is a fairly trivial question, but I would like to make sure that I haven't overlooked anything.
Here is an example of what I mean.
The span(v1,v2), where v_{1} = \left(\begin{array}{cc}1\\0\end{array}\right), v_{2} = \left(\begin{array}{cc}0\\1\end{array}\right) is R2. It is also closed under addition and multiplication, and contains the zero vector, so it satisfies the requirements for a subspace; is it a subspace within, say Rn with n>2? I don't think so, because the vector is composed of two components, and I was thinking a subspace would have to be within the confines of these two dimensions.
Any help appreciated, if it is not clear I can try to re-explain what I mean. I am hoping it's more of an issue of definition.
Thanks in advance.
 
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nobahar said:
Hello!
Just a quick question. Is the following okay?:
The span of a set of vectors corresponds to a subspace in Rn.
But the span of a set of vectors can also be ALL of Rn, does that mean all of Rn can be considered a subspace?
Yes, a vector space is a subspace of itself.
 
\mathbb{R}^n is a subspace of itself (you can verify with the definition that it satisfies the properties of a subspace).
 
Thankyou Vela and Rasmhop.
 
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