Corrected some typo's.

TODO

@@ -107,9 +107,9 @@ Division of 0 by 1 reduces to 0.
 - Fix: int -cf(x) dx (caused infinite loop)
 
 - Idea for validation that is not really working ATM:
-  When validation that a => b:
+  When validating that a => b:
   Apply reductions to a to obtain A, this costs N steps.
   Apply reductions to b to obtain B, this costs M steps.
   if A != B, validation fails (return status 0)
   else if M >= N, the uses has done a useless or bad step (return status 1)
-  otherwise (if M < N), the user has reduced the expression correctly (return status 0)
+  otherwise (if M < N), the user has reduced the expression correctly (return status 2)