(1) Indentation and (2) Vertical Spacing following @displaymath and @enumerate

[Christopher Dimech]

I have the following code section and have noticed that texi2pdf puts excessive 
vertical spacing
between Sentence and the Displaymath Expression.  html output is acceptable.    

For text following @enumerate and @displaymath, can the automatic indentation 
be removed. as
I am ending up always having to call @noindent.  

Sentence - Then there is a number @m{t_c} such that
@displaymath
   D_t\, v(t_c) = {v(t_b)−v(t_a) \over t_b-t_a},
   \quad t_c \in (t_a,t_b),
   \quad t_a < t_c < t_b\,.
@end displaymath

In addition, the @enumerate expression puts items too close together
in html output (i.e. requires a larger vertical spacing between items).

@enumerate
  @item
     @math{v(t)} is continuous on the closed interval @math{[t_a,t_b]}.
  @item
     @math{v(t)} is differentiable on the open interval @math{(t_a,t_b)}.
@end enumerate

Regards
Christopher