Correct align environment in notes

notes/inversive.md

@@ -47,11 +47,13 @@ One conceivable way to canonicalize lines is to use the *perpendicular* plane th
 The coordinate conventions used in the engine are different from the ones used in these notes. Marking the engine vectors and coordinates with $'$, we have
 $$I' = (x', y', z', b', c'),$$
 where
-$$\begin{align*}
+$$
+\begin{align*}
 x' & = x & b' & = b/2 \\
 y' & = y & c' & = c/2. \\
 z' & = z
-\end{align*}$$
+\end{align*}
+$$
 The engine uses the quadratic form $Q' = -Q$, which is expressed in engine coordinates as
 $$Q'(I'_1, I'_2) = x'_1 x'_2 + y'_1 y'_2 + z'_1 z'_2 - 2(b'_1c'_2 + c'_1 b'_2).$$
 In the `engine` module, the matrix of $Q'$ is encoded in the lazy static variable `Q`.