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Fixes math rendering in doc.
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jkeeley-MW committed Oct 3, 2024
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14 changes: 7 additions & 7 deletions documentation/AI-Verification-Convexity.md
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Expand Up @@ -209,8 +209,8 @@ $\mathrm{sgn}(\nabla f(a), -\nabla f(b))=(\pm,\pm)$. Note that the sign of 0 is
taken as positive in this discussion.

If $f$ is differentiable at the interval bounds, then there are two possible
sign combinations since $ \nabla f(a)\leq m \lt 0 $ where $m$ is the gradient
of the chord.
sign combinations since $\nabla{f(a)}\leq{m}\lt{0}$ where $m$ is the gradient of
the chord.

- $\mathrm{sgn}(\nabla f(a), -\nabla f(b))=(−,+)$, then the minimum must lie at
$x=b$, i.e., $f(x)\geq{f(b)}$.
Expand Down Expand Up @@ -266,7 +266,7 @@ f(b+\epsilon) \lt -\nabla f(b-\epsilon) \leq -m \lt 0$.

In the case that $f(a)=f(b)$, the function must either be constant and the
minimum is $f(a)=f(b)$. Or the minimum again lies at the interior. If
$\mathrm{sgn}(\nabla f(a))=+$, then $\nabla f(a) = 0$ else this violates
$\mathrm{sgn}(\nabla f(a))=+$, then $\nabla{f(a)}=0$ else this violates
convexity since $f(a)=f(b)$. Similar is true for $-\mathrm{sgn}(\nabla f(b))=+$.
In this case, all sign combinations are possible owing to possible
non-differentiability of $f$ at the interval bounds:
Expand Down Expand Up @@ -321,7 +321,7 @@ discussed later.
An important property of convex functions in n-dimensions is that every
1-dimension restriction also defines a convex function. This is easily seen from
the definition. Define $g:\mathbb{R}\rightarrow\mathbb{R}$ as $g(t)
=f(t\hat{n})$ where $\hat{n}$ is some unit vector in $\mathbb{R}^n$. Then, by
=f(t\hat{n})$ where $`\hat{n}`$ is some unit vector in $\mathbb{R}^n$. Then, by
definition of convexity of $f$, letting $x=t\hat{n}$ and $y=t'\hat{n}$, it
follows that,

Expand Down Expand Up @@ -370,7 +370,7 @@ along an edge. Figure 6 summarizes this construction on a cube.
</figure>

Analogous to the 1-dimensional case, analyze the signatures of the derivatives
at the vertices. The notation $(\pm,...,\pm)_v $ denotes the overall sign of
at the vertices. The notation $(\pm,...,\pm)_v$ denotes the overall sign of
$−\mathrm{sgn}(v_i)\nabla_i f(v)$ at $v$ for each $i$, and is used in the rest
of this article.

Expand All @@ -382,7 +382,7 @@ minimum value of *f* over the hypercube.
**Proof**:

For any point $z \in H_n$, construct the line containing $w$ and $z$, given by
$L=\{w+t\hat{n}|t \in \mathbb{R}\}$, where $\hat{n}$ is a unit vector in
$L=\{w+t\hat{n}|t \in \mathbb{R}\}$, where $`\hat{n}`$ is a unit vector in
direction $z-w$. Since the directional derivatives at $w$ pointing inwards are
all positive, and $f$ is differentiable, the derivative along the line at $w$,
pointing inwards, is given by,
Expand Down Expand Up @@ -430,7 +430,7 @@ Figure 7.
</figure>

As depicted in figure 7, the vertices $w$ of the square (hypercube of dimension
two, $V_2 = \{\pm 1,\pm 1\}$), have directional derivatives of zero and thus
two, $V_2=\{\pm 1,\pm 1\}$), have directional derivatives of zero and thus
signature $(+,+)$. But the derivative along any direction bisecting these
directional derivatives, into the interior of the square, has a negative
gradient. This is because the vertex is at the intersection of two planes and is
Expand Down

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