align fix; theorem style; condition number

quarto/differentiable_vector_calculus/vectors.qmd

@@ -443,12 +443,13 @@ $$
 
 The left hand sides are in the form of a dot product, in this case $\langle a,b \rangle \cdot \langle x, y\rangle$ and  $\langle a,b,c \rangle \cdot \langle x, y, z\rangle$ respectively. When there is a system of equations, something like:
 
-
+$$
 \begin{align*}
 3x  &+ 4y  &- 5z &= 10\\
 3x  &- 5y  &+ 7z &= 11\\
 -3x &+ 6y  &+ 9z &= 12,
 \end{align*}
+$$
 
 Then we might think of $3$ vectors $\langle 3,4,-5\rangle$, $\langle 3,-5,7\rangle$, and $\langle -3,6,9\rangle$ being dotted with $\langle x,y,z\rangle$. Mathematically, matrices and their associated algebra are used to represent this. In this example, the system of equations above would be represented by a matrix and two vectors: