sb-eqat<w

Theorem.

Arguments:

x (sv), y (st), z (st),

Distinct variable conditions:

(x, z), (x, y),

Assertions:

([z/x](xeqy)leftrightarrow(zeqy))

Proof:

Hyp Ref Line Expr
ax17-bv1(x bound in (zeqy))
eqt<2((xeqz)to((xeqy)leftrightarrow(zeqy)))
1, 2sb-xplw3([z/x](xeqy)leftrightarrow(zeqy))