theorem Th11: :: BORSUK_6:11

for S, T being Subset of (TOP-REAL 2) st S = { p where p is Point of (TOP-REAL 2) : p `2 >= (2 * (p `1)) - 1 } & T = { p where p is Point of (TOP-REAL 2) : p `2 >= p `1 } holds
(AffineMap (1,0,(1 / 2),(1 / 2))) .: S = T