More typos.

Do they ever end?

06_Multivariate_Kalman_Filters.ipynb

@@ -8779,7 +8779,7 @@
     "We already talked about the symmetry of the covariance matrix; $\\sigma_{ab}=\\sigma_{ba}$. We see now why this is true from the equation for the covariance.\n",
     "\n",
     "$$\\begin{aligned} COV(x,y) &= \\frac{1}{N}\\sum_{i=1}^N (x_i - \\mu_x)(y_i - \\mu_y) \\\\\n",
-    "&= \\frac{1}{N}\\sum_{i=1}^N (y_i - \\mu_y)(x_i - \\mu_x \\\\\n",
+    "&= \\frac{1}{N}\\sum_{i=1}^N (y_i - \\mu_y)(x_i - \\mu_x) \\\\\n",
     "&= COV(y,x)\\end{aligned}$$\n",
     "\n",
     "This gives the covariance matrix\n",