diff --git a/08_Designing_Kalman_Filters.ipynb b/08_Designing_Kalman_Filters.ipynb
index dbfa803..d642fd3 100644
--- a/08_Designing_Kalman_Filters.ipynb
+++ b/08_Designing_Kalman_Filters.ipynb
@@ -1,7 +1,7 @@
 {
  "metadata": {
   "name": "",
-  "signature": "sha256:51f7b58d6afaa72d40acf2ef271113702aca242a6daeefd79d8303d6f2d98fef"
+  "signature": "sha256:5b914d2819c79c26bfdf017e0bbecef1f2eef75116579a5d9e29dbde88d150bb"
  },
  "nbformat": 3,
  "nbformat_minor": 0,
@@ -1158,7 +1158,7 @@
       "\n",
       "So now we have to design our state transition. The Newtonian equations for a time step are:\n",
       "\n",
-      "$$\\begin{aligned} x_t &= x_{t-1} + v\\Delta t + 0.5a_{t-1} \\Delta t^2 \\\\\n",
+      "$$\\begin{aligned} x_t &= x_{t-1} + v_{t-1}\\Delta t + 0.5a_{t-1} \\Delta t^2 \\\\\n",
       " v_t &= v_{t-1} \\Delta t + a_{t-1} \\\\\n",
       " a_t &= a_{t-1}\\end{aligned}$$\n",
       " \n",