DEFINITION sty0_gen_appl()
TYPE =
       ∀g:G
         .∀c:C
           .∀u:T
             .∀t1:T
               .∀x:T
                 .sty0 g c (THead (Flat Appl) u t1) x
                   →ex2 T λt2:T.sty0 g c t1 t2 λt2:T.eq T x (THead (Flat Appl) u t2)
BODY =
        assume g: G
        assume c: C
        assume u: T
        assume t1: T
        assume x: T
        suppose H: sty0 g c (THead (Flat Appl) u t1) x
           assume y: T
           suppose H0: sty0 g c y x
             we proceed by induction on H0 to prove 
                eq T y (THead (Flat Appl) u t1)
                  →ex2 T λt2:T.sty0 g c t1 t2 λt2:T.eq T x (THead (Flat Appl) u t2)
                case sty0_sort : c0:C n:nat ⇒
                   the thesis becomes 
                   ∀H1:eq T (TSort n) (THead (Flat Appl) u t1)
                     .ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (TSort (next g n)) (THead (Flat Appl) u t2)
                      suppose H1: eq T (TSort n) (THead (Flat Appl) u t1)
                         (H2) 
                            we proceed by induction on H1 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒True
                                 | TLRef ⇒False
                                 | THead   ⇒False
                               case refl_equal : ⇒
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TSort n OF
                                      TSort ⇒True
                                    | TLRef ⇒False
                                    | THead   ⇒False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TSort n OF
                                            TSort ⇒True
                                          | TLRef ⇒False
                                          | THead   ⇒False

                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒True
                                 | TLRef ⇒False
                                 | THead   ⇒False
                         end of H2
                         consider H2
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Appl) u t1 OF
                                TSort ⇒True
                              | TLRef ⇒False
                              | THead   ⇒False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (TSort (next g n)) (THead (Flat Appl) u t2)
                         we proved ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (TSort (next g n)) (THead (Flat Appl) u t2)

                         ∀H1:eq T (TSort n) (THead (Flat Appl) u t1)
                           .ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (TSort (next g n)) (THead (Flat Appl) u t2)
                case sty0_abbr : c0:C d:C v:T i:nat :getl i c0 (CHead d (Bind Abbr) v) w:T :sty0 g d v w ⇒
                   the thesis becomes 
                   ∀H4:eq T (TLRef i) (THead (Flat Appl) u t1)
                     .ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O w) (THead (Flat Appl) u t2)
                   () by induction hypothesis we know 
                      eq T v (THead (Flat Appl) u t1)
                        →ex2 T λt2:T.sty0 g d t1 t2 λt2:T.eq T w (THead (Flat Appl) u t2)
                      suppose H4: eq T (TLRef i) (THead (Flat Appl) u t1)
                         (H5) 
                            we proceed by induction on H4 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒True
                                 | THead   ⇒False
                               case refl_equal : ⇒
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TLRef i OF
                                      TSort ⇒False
                                    | TLRef ⇒True
                                    | THead   ⇒False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TLRef i OF
                                            TSort ⇒False
                                          | TLRef ⇒True
                                          | THead   ⇒False

                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒True
                                 | THead   ⇒False
                         end of H5
                         consider H5
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Appl) u t1 OF
                                TSort ⇒False
                              | TLRef ⇒True
                              | THead   ⇒False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O w) (THead (Flat Appl) u t2)
                         we proved ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O w) (THead (Flat Appl) u t2)

                         ∀H4:eq T (TLRef i) (THead (Flat Appl) u t1)
                           .ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O w) (THead (Flat Appl) u t2)
                case sty0_abst : c0:C d:C v:T i:nat :getl i c0 (CHead d (Bind Abst) v) w:T :sty0 g d v w ⇒
                   the thesis becomes 
                   ∀H4:eq T (TLRef i) (THead (Flat Appl) u t1)
                     .ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O v) (THead (Flat Appl) u t2)
                   () by induction hypothesis we know 
                      eq T v (THead (Flat Appl) u t1)
                        →ex2 T λt2:T.sty0 g d t1 t2 λt2:T.eq T w (THead (Flat Appl) u t2)
                      suppose H4: eq T (TLRef i) (THead (Flat Appl) u t1)
                         (H5) 
                            we proceed by induction on H4 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒True
                                 | THead   ⇒False
                               case refl_equal : ⇒
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE TLRef i OF
                                      TSort ⇒False
                                    | TLRef ⇒True
                                    | THead   ⇒False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE TLRef i OF
                                            TSort ⇒False
                                          | TLRef ⇒True
                                          | THead   ⇒False

                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒True
                                 | THead   ⇒False
                         end of H5
                         consider H5
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Appl) u t1 OF
                                TSort ⇒False
                              | TLRef ⇒True
                              | THead   ⇒False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O v) (THead (Flat Appl) u t2)
                         we proved ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O v) (THead (Flat Appl) u t2)

                         ∀H4:eq T (TLRef i) (THead (Flat Appl) u t1)
                           .ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T (lift (S i) O v) (THead (Flat Appl) u t2)
                case sty0_bind : b:B c0:C v:T t0:T t2:T :sty0 g (CHead c0 (Bind b) v) t0 t2 ⇒
                   the thesis becomes 
                   ∀H3:eq T (THead (Bind b) v t0) (THead (Flat Appl) u t1)
                     .ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Appl) u t3)
                   () by induction hypothesis we know 
                      eq T t0 (THead (Flat Appl) u t1)
                        →ex2 T λt3:T.sty0 g (CHead c0 (Bind b) v) t1 t3 λt3:T.eq T t2 (THead (Flat Appl) u t3)
                      suppose H3: eq T (THead (Bind b) v t0) (THead (Flat Appl) u t1)
                         (H4) 
                            we proceed by induction on H3 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒False
                                 | THead k  ⇒<λ:K.Prop> CASE k OF Bind ⇒True | Flat ⇒False
                               case refl_equal : ⇒
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Bind b) v t0 OF
                                      TSort ⇒False
                                    | TLRef ⇒False
                                    | THead k  ⇒<λ:K.Prop> CASE k OF Bind ⇒True | Flat ⇒False
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Bind b) v t0 OF
                                            TSort ⇒False
                                          | TLRef ⇒False
                                          | THead k  ⇒<λ:K.Prop> CASE k OF Bind ⇒True | Flat ⇒False

                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒False
                                 | THead k  ⇒<λ:K.Prop> CASE k OF Bind ⇒True | Flat ⇒False
                         end of H4
                         consider H4
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Appl) u t1 OF
                                TSort ⇒False
                              | TLRef ⇒False
                              | THead k  ⇒<λ:K.Prop> CASE k OF Bind ⇒True | Flat ⇒False
                         that is equivalent to False
                         we proceed by induction on the previous result to prove ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Appl) u t3)
                         we proved ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Appl) u t3)

                         ∀H3:eq T (THead (Bind b) v t0) (THead (Flat Appl) u t1)
                           .ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Bind b) v t2) (THead (Flat Appl) u t3)
                case sty0_appl : c0:C v:T t0:T t2:T H1:sty0 g c0 t0 t2 ⇒
                   the thesis becomes 
                   ∀H3:eq T (THead (Flat Appl) v t0) (THead (Flat Appl) u t1)
                     .ex2
                       T
                       λt3:T.sty0 g c0 t1 t3
                       λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Appl) u t3)
                   (H2) by induction hypothesis we know 
                      eq T t0 (THead (Flat Appl) u t1)
                        →ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T t2 (THead (Flat Appl) u t3)
                      suppose H3: eq T (THead (Flat Appl) v t0) (THead (Flat Appl) u t1)
                         (H4) 
                            by (f_equal . . . . . H3)
                            we proved 
                               eq
                                 T
                                 <λ:T.T>
                                   CASE THead (Flat Appl) v t0 OF
                                     TSort ⇒v
                                   | TLRef ⇒v
                                   | THead  t ⇒t
                                 <λ:T.T>
                                   CASE THead (Flat Appl) u t1 OF
                                     TSort ⇒v
                                   | TLRef ⇒v
                                   | THead  t ⇒t

                               eq
                                 T
                                 λe:T.<λ:T.T> CASE e OF TSort ⇒v | TLRef ⇒v | THead  t ⇒t
                                   THead (Flat Appl) v t0
                                 λe:T.<λ:T.T> CASE e OF TSort ⇒v | TLRef ⇒v | THead  t ⇒t
                                   THead (Flat Appl) u t1
                         end of H4
                         (h1) 
                            (H5) 
                               by (f_equal . . . . . H3)
                               we proved 
                                  eq
                                    T
                                    <λ:T.T> CASE THead (Flat Appl) v t0 OF TSort ⇒t0 | TLRef ⇒t0 | THead   t⇒t
                                    <λ:T.T> CASE THead (Flat Appl) u t1 OF TSort ⇒t0 | TLRef ⇒t0 | THead   t⇒t

                                  eq
                                    T
                                    λe:T.<λ:T.T> CASE e OF TSort ⇒t0 | TLRef ⇒t0 | THead   t⇒t
                                      THead (Flat Appl) v t0
                                    λe:T.<λ:T.T> CASE e OF TSort ⇒t0 | TLRef ⇒t0 | THead   t⇒t
                                      THead (Flat Appl) u t1
                            end of H5
                            suppose H6: eq T v u
                               (H8) 
                                  consider H5
                                  we proved 
                                     eq
                                       T
                                       <λ:T.T> CASE THead (Flat Appl) v t0 OF TSort ⇒t0 | TLRef ⇒t0 | THead   t⇒t
                                       <λ:T.T> CASE THead (Flat Appl) u t1 OF TSort ⇒t0 | TLRef ⇒t0 | THead   t⇒t
                                  that is equivalent to eq T t0 t1
                                  we proceed by induction on the previous result to prove sty0 g c0 t1 t2
                                     case refl_equal : ⇒
                                        the thesis becomes the hypothesis H1
sty0 g c0 t1 t2
                               end of H8
                               by (refl_equal . .)
                               we proved eq T (THead (Flat Appl) u t2) (THead (Flat Appl) u t2)
                               by (ex_intro2 . . . . H8 previous)
                               we proved 
                                  ex2
                                    T
                                    λt3:T.sty0 g c0 t1 t3
                                    λt3:T.eq T (THead (Flat Appl) u t2) (THead (Flat Appl) u t3)
                               by (eq_ind_r . . . previous . H6)
                               we proved 
                                  ex2
                                    T
                                    λt3:T.sty0 g c0 t1 t3
                                    λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Appl) u t3)

                               eq T v u
                                 →(ex2
                                      T
                                      λt3:T.sty0 g c0 t1 t3
                                      λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Appl) u t3))
                         end of h1
                         (h2) 
                            consider H4
                            we proved 
                               eq
                                 T
                                 <λ:T.T>
                                   CASE THead (Flat Appl) v t0 OF
                                     TSort ⇒v
                                   | TLRef ⇒v
                                   | THead  t ⇒t
                                 <λ:T.T>
                                   CASE THead (Flat Appl) u t1 OF
                                     TSort ⇒v
                                   | TLRef ⇒v
                                   | THead  t ⇒t
eq T v u
                         end of h2
                         by (h1 h2)
                         we proved 
                            ex2
                              T
                              λt3:T.sty0 g c0 t1 t3
                              λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Appl) u t3)

                         ∀H3:eq T (THead (Flat Appl) v t0) (THead (Flat Appl) u t1)
                           .ex2
                             T
                             λt3:T.sty0 g c0 t1 t3
                             λt3:T.eq T (THead (Flat Appl) v t2) (THead (Flat Appl) u t3)
                case sty0_cast : c0:C v1:T v2:T :sty0 g c0 v1 v2 t0:T t2:T :sty0 g c0 t0 t2 ⇒
                   the thesis becomes 
                   ∀H5:eq T (THead (Flat Cast) v1 t0) (THead (Flat Appl) u t1)
                     .ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Appl) u t3)
                   () by induction hypothesis we know 
                      eq T v1 (THead (Flat Appl) u t1)
                        →ex2 T λt2:T.sty0 g c0 t1 t2 λt2:T.eq T v2 (THead (Flat Appl) u t2)
                   () by induction hypothesis we know 
                      eq T t0 (THead (Flat Appl) u t1)
                        →ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T t2 (THead (Flat Appl) u t3)
                      suppose H5: eq T (THead (Flat Cast) v1 t0) (THead (Flat Appl) u t1)
                         (H6) 
                            we proceed by induction on H5 to prove 
                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒False
                                 | THead k  ⇒
                                       <λ:K.Prop>
                                         CASE k OF
                                           Bind ⇒False
                                         | Flat f⇒<λ:F.Prop> CASE f OF Appl⇒False | Cast⇒True
                               case refl_equal : ⇒
                                  the thesis becomes 
                                  <λ:T.Prop>
                                    CASE THead (Flat Cast) v1 t0 OF
                                      TSort ⇒False
                                    | TLRef ⇒False
                                    | THead k  ⇒
                                          <λ:K.Prop>
                                            CASE k OF
                                              Bind ⇒False
                                            | Flat f⇒<λ:F.Prop> CASE f OF Appl⇒False | Cast⇒True
                                     consider I
                                     we proved True

                                        <λ:T.Prop>
                                          CASE THead (Flat Cast) v1 t0 OF
                                            TSort ⇒False
                                          | TLRef ⇒False
                                          | THead k  ⇒
                                                <λ:K.Prop>
                                                  CASE k OF
                                                    Bind ⇒False
                                                  | Flat f⇒<λ:F.Prop> CASE f OF Appl⇒False | Cast⇒True

                               <λ:T.Prop>
                                 CASE THead (Flat Appl) u t1 OF
                                   TSort ⇒False
                                 | TLRef ⇒False
                                 | THead k  ⇒
                                       <λ:K.Prop>
                                         CASE k OF
                                           Bind ⇒False
                                         | Flat f⇒<λ:F.Prop> CASE f OF Appl⇒False | Cast⇒True
                         end of H6
                         consider H6
                         we proved 
                            <λ:T.Prop>
                              CASE THead (Flat Appl) u t1 OF
                                TSort ⇒False
                              | TLRef ⇒False
                              | THead k  ⇒
                                    <λ:K.Prop>
                                      CASE k OF
                                        Bind ⇒False
                                      | Flat f⇒<λ:F.Prop> CASE f OF Appl⇒False | Cast⇒True
                         that is equivalent to False
                         we proceed by induction on the previous result to prove 
                            ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Appl) u t3)
                         we proved 
                            ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Appl) u t3)

                         ∀H5:eq T (THead (Flat Cast) v1 t0) (THead (Flat Appl) u t1)
                           .ex2 T λt3:T.sty0 g c0 t1 t3 λt3:T.eq T (THead (Flat Cast) v2 t2) (THead (Flat Appl) u t3)
             we proved 
                eq T y (THead (Flat Appl) u t1)
                  →ex2 T λt2:T.sty0 g c t1 t2 λt2:T.eq T x (THead (Flat Appl) u t2)
          we proved 
             ∀y:T
               .sty0 g c y x
                 →(eq T y (THead (Flat Appl) u t1)
                      →ex2 T λt2:T.sty0 g c t1 t2 λt2:T.eq T x (THead (Flat Appl) u t2))
          by (insert_eq . . . . previous H)
          we proved ex2 T λt2:T.sty0 g c t1 t2 λt2:T.eq T x (THead (Flat Appl) u t2)
       we proved 
          ∀g:G
            .∀c:C
              .∀u:T
                .∀t1:T
                  .∀x:T
                    .sty0 g c (THead (Flat Appl) u t1) x
                      →ex2 T λt2:T.sty0 g c t1 t2 λt2:T.eq T x (THead (Flat Appl) u t2)