Let x0 of type ι be given.
Let x1 of type ι be given.
Let x2 of type ι be given.
Apply andE with
In x2 x0,
In x2 x1.
Apply unknownprop_6e872934bf94cf597caad1f424704613be52b8af8705e5e9337ebcf0b7f41fff with
x0,
x1,
x2.
The subproof is completed by applying H0.