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Update EV6 class activities to clarify spanning R^n and spanning subspace#933

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jkostiuk merged 7 commits intomainfrom
StevenClontz-patch-35
Feb 18, 2026
Merged

Update EV6 class activities to clarify spanning R^n and spanning subspace#933
jkostiuk merged 7 commits intomainfrom
StevenClontz-patch-35

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@StevenClontz
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This is basically the explanation I came up with on the fly today; will try it in my 11am class in a few minutes...

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@siwelwerd
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will try it in my 11am class in a few minutes...

Perhaps we should await your reflection on its implementation before reviewing then.

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Yeah I meant to set this as draft until that happened.

But I thought it went quite well. I went from no teams realizing that the vectors still span the subspace, to half of the teams making that connection. So the conversation was much better. I don't think I have any further tweaks other than a typo or two I'll address now.

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@StevenClontz StevenClontz marked this pull request as draft February 18, 2026 18:38
Comment on lines 262 to 275
Similarly,
<me>
\setList{
\left[\begin{array}{c}1\\2\\3\end{array}\right],
\left[\begin{array}{c}-2\\0\\5\end{array}\right]
}
\text{ and }
\setList{
\left[\begin{array}{c}-1\\2\\8\end{array}\right],
\left[\begin{array}{c}0\\4\\11\end{array}\right]
}
</me>
are both valid bases for the same planar subspace of <m>\IR^3</m>,
and they both contain two vectors.
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Actually here's one more hiccup I fixed on the fly in both classes that I'll fix here now: we emphasize that every basis for $\mathbb R^3$ has three vectors, but I think it's helpful to emphasize this for a planar subspace as well (since subspace dimension is what we're doing in our assessments).

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@StevenClontz StevenClontz marked this pull request as ready for review February 18, 2026 18:48
@StevenClontz StevenClontz marked this pull request as draft February 18, 2026 18:49
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Comment on lines 235 to 241
<definition>
<statement>
<p>
Any non-trivial real vector space has infinitely-many different bases, but all
the bases for a given vector space are exactly the same size.
</p>
<p>
For example,
<me>
\setList{\vec e_1,\vec e_2,\vec e_3}
\text{ and }
\setList{
\left[\begin{array}{c}1\\0\\0\end{array}\right],
\left[\begin{array}{c}0\\1\\0\end{array}\right],
\left[\begin{array}{c}1\\1\\1\end{array}\right]
}
\text{ and }
\setList{
\left[\begin{array}{c}1\\0\\-3\end{array}\right],
\left[\begin{array}{c}2\\-2\\1\end{array}\right],
\left[\begin{array}{c}3\\-2\\5\end{array}\right]
}
</me>
are all valid bases for <m>\IR^3</m>, and they all contain three vectors.
</p>
<p>
Similarly,
<me>
\setList{
\left[\begin{array}{c}1\\2\\3\end{array}\right],
\left[\begin{array}{c}-2\\0\\5\end{array}\right]
}
\text{ and }
\setList{
\left[\begin{array}{c}-1\\2\\8\end{array}\right],
\left[\begin{array}{c}0\\4\\11\end{array}\right]
}
</me>
are both valid bases for the same planar subspace of <m>\IR^3</m>,
and they both contain two vectors.
</p>
</statement>
</fact>

<definition>
<statement>
<p>
The <term>dimension</term> of a vector space or subspace is equal to the size
of any basis for the vector space.
So we say the <term>dimension</term> of a vector space or subspace is equal to the
size of any basis for the vector space.
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Rather than having two very similar blocks, I've combined the observation that every basis has the same size into the definition of dimension.

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@StevenClontz StevenClontz marked this pull request as ready for review February 18, 2026 19:07
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Okay now I'm really ready

Co-authored-by: jkostiuk <kostiuk.jordan@gmail.com>
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@jkostiuk jkostiuk merged commit 787f1cb into main Feb 18, 2026
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3 participants