Goal:
  
  A : Type
  f : A -> bool
  g : A -> bool
  a : A
  Hf : forall x : A, f x -> g x
  H : is_true (foroptb f (Some a))
  ============================
   (is_true (foroptb g (Some a)))


DEBUG:Going to execute:
do
![ solve
 [ trivial | apply : eq_sym ; trivial ]
 | discriminate
 | contradiction
 | split ]