Let x0 of type ο be given.
Let x1 of type ο be given.
Let x2 of type ο be given.
Assume H0: x0.
Apply orIL with
and (exactly1of2 x0 x1) (not x2),
and (and (not x0) (not x1)) x2.
Apply andI with
exactly1of2 x0 x1,
not x2 leaving 2 subgoals.
Apply exactly1of2_I1 with
x0,
x1 leaving 2 subgoals.
The subproof is completed by applying H0.
The subproof is completed by applying H1.
The subproof is completed by applying H2.