Update week1.do.txt

Author: mhjensen

doc/src/week1/week1.do.txt

@@ -363,7 +363,7 @@ and
 With a given vector $\vert x \rangle$, we define the inner product as
 !bt
 \[
-\langle x \vert x\rangle = \sum_{i=0}^{n-1} x_i^*x_i=x_0^2+x_1^2+\dots + x_{n-1}^2. 
+\langle x \vert x\rangle = \sum_{i=0}^{n-1} x_i^*x_i=\vert x_0\vert^2+\vert x_1\vert ^2+\dots + \vert x_{n-1}\vert^2. 
 \]
 !et