Typo reference manual

doc/refman/RefMan-tacex.tex

@@ -64,7 +64,7 @@
 
 As the hypothesis itself did not appear in the goal, we did not need to
 use an heterogeneous equality to relate the new hypothesis to the old
-one (which just disappeared here). However, the tactic works just a well
+one (which just disappeared here). However, the tactic works just as well
 in this case, e.g.:
 
 \begin{coq_eval}