theorem eq_f2: \forall A,B,C:Type.\forall f:A\to B \to C.
\forall x1,x2:A. \forall y1,y2:B.
x1=x2 \to y1=y2 \to f x1 y1 = f x2 y2.
theorem eq_f2: \forall A,B,C:Type.\forall f:A\to B \to C.
\forall x1,x2:A. \forall y1,y2:B.
x1=x2 \to y1=y2 \to f x1 y1 = f x2 y2.