Fix typo in lab 1

Author: Ahmkel

lab1_FFN/lab1_FFN.ipynb

@@ -284,7 +284,7 @@
    "source": [
     "To train our neural network we need to update the parameters in direction of the negative gradient w.r.t the cost function we defined earlier.\n",
     "We can use `tf.train.Optimizer` to get the gradients (using `compute_gradients`) for all parameters in the network w.r.t ``cost_train``.\n",
-    "Imaggine that `cost_train` is a function and we want to go downhill. We go downhill by changing the value of the paramters in direction of the negative gradient. \n",
+    "Imagine that `cost_train` is a function and we want to go downhill. We go downhill by changing the value of the paramters in direction of the negative gradient. \n",
     "\n",
     "Finally we can use the built-in `minimize` to calculate the stochastic gradient descent (SGD) update rule for each paramter in the network.\n",
     "\n",