import Int. variable a : Int variable P : Int -> Int -> Bool variable f : Int -> Int -> Int variable g : Int -> Int axiom H1 : P (f a (g a)) (f a (g a)) axiom H2 : P (f (g a) (g a)) (f (g a) (g a)) axiom H3 : P (f (g a) (g a)) (g a) theorem T1 : exists x y : Int, P (f y x) (f y x) := exists::intro _ (exists::intro _ H1) theorem T2 : exists x : Int, P (f x (g x)) (f x (g x)) := exists::intro _ H1 theorem T3 : exists x : Int, P (f x x) (f x x) := exists::intro _ H2 theorem T4 : exists x : Int, P (f (g a) x) (f x x) := exists::intro _ H2 theorem T5 : exists x : Int, P x x := exists::intro _ H2 theorem T6 : exists x y : Int, P x y := exists::intro _ (exists::intro _ H3) theorem T7 : exists x : Int, P (f x x) x := exists::intro _ H3 theorem T8 : exists x y : Int, P (f x x) y := exists::intro _ (exists::intro _ H3) print environment 8.