let x, y be Element of 2; :: thesis: Set_to_zero . (x,y) = 0
A1: [x,y] in [:2,2:] by ZFMISC_1:87;
thus Set_to_zero . (x,y) = Set_to_zero . [x,y]
.= 0 by A1, FUNCOP_1:7 ; :: thesis: verum