Let x0 of type ι be given.
Apply binunionI2 with
x0,
Sing (Sing 2),
Sing 2.
The subproof is completed by applying SingI with
Sing 2.
Apply unknownprop_7bb148020ac74fad9e588d8f6f24c2245db7c295ea73aac9a7af2c90be710bd6.
Apply ordinal_Hered with
(λ x1 . SetAdjoin x1 (Sing 2)) x0,
Sing 2 leaving 2 subgoals.
The subproof is completed by applying H0.
The subproof is completed by applying L1.