let G be V9() Matrix of (TOP-REAL 2); :: thesis: ( G is Y_equal-in-column implies h_strip (G,0) = { |[r,s]| where r, s is Real : s <= (G * (1,1)) `2 } )

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,0) = { |[r,s]| where r, s is Real : s <= (G * (1,1)) `2 }

hence h_strip (G,0) = { |[r,s]| where r, s is Real : s <= (G * (1,1)) `2 } by A1, GOBOARD5:7; :: thesis: verum

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,0) = { |[r,s]| where r, s is Real : s <= (G * (1,1)) `2 }

hence h_strip (G,0) = { |[r,s]| where r, s is Real : s <= (G * (1,1)) `2 } by A1, GOBOARD5:7; :: thesis: verum