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While this is on the front page, removing redundant whitespace introduced to prevent "too few changes"
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LSpice
LSpice
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Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$. $\ \ \ \ $

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$. $\ \ \ \ $

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$.

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Removed a LaTeX remark. The strange $\ \ \ \ $ is to avoid the "too few changes" restriction.
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Yuichiro Fujiwara
Yuichiro Fujiwara
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Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$. $\ \ \ \ $

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$.

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$. $\ \ \ \ $

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

remove the silly and incomprehensible LaTeX remark
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edit approved Jan 7, 2015 at 9:48
Community Bot
edit approved Jan 7, 2015 at 9:48
Community Bot
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Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{v_0\cdot v<0\}$ (for the brace, enclose your latex expression with )$\{\,v\mid v_0\cdot v<0\,\}$.

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{v_0\cdot v=0\}$$\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{v_0\cdot v<0\}$ (for the brace, enclose your latex expression with ).

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{v_0\cdot v=0\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

Let us prove by induction that this number is $n+1$. The result is obvious for $n=1$. Assume it for some $n$ and consider a set of mutually negative dot product vectors $v_0,v_1,\ldots, v_k$ in $\mathbb{R}^{n+1}$. Then all of $v_1,\ldots,v_k$ lie in the open half-space $\{\,v\mid v_0\cdot v<0\,\}$.

Now the orthogonal projections $v_i'$ of $v_i$ ($1\leqslant i\leqslant k$) on the hyperplane $\{\,v\mid v_0\cdot v=0\,\}$ satisfy $v_i'\cdot v_j'\leqslant v_i\cdot v_j$ by a direct computation (assuming $v_i$ are unitary, one has $v_i'=v_i-(v_i\cdot v_0)v_0$ so that $v_i'\cdot v_j' = v_i\cdot v_j-(v_i\cdot v_0)(v_j\cdot v_0)$). By induction $k$ is at most $n+1$ and we are done.

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Benoît Kloeckner
Benoît Kloeckner
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