let G be V9() 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 } )
assume A1: 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 }
0 <> len G by GOBOARD1:def 5;
then 1 <= len G by NAT_1:14;
hence h_strip G,(width G) = { |[r,s]| where r, s is Real : (G * 1,(width G)) `2 <= s } by A1, GOBOARD5:7; :: thesis: verum