let G be empty-yielding Matrix of (TOP-REAL 2); :: thesis: ( G is Y_equal-in-column implies h_strip (G,(width G)) = { |[r,s]| where r, s is Real : (G * (1,(width G))) `2 <= s } )
0 <> len G by MATRIX_0:def 10;
then A1: 1 <= len G by NAT_1:14;
assume G is Y_equal-in-column ; :: thesis: h_strip (G,(width G)) = { |[r,s]| where r, s is Real : (G * (1,(width G))) `2 <= s }
hence h_strip (G,(width G)) = { |[r,s]| where r, s is Real : (G * (1,(width G))) `2 <= s } by A1, GOBOARD5:6; :: thesis: verum