from X cons X from s X 2ndspos 0 Z rnil 2ndspos s N cons X Z 2ndspos s N cons2 X Z 2ndspos s N cons2 X cons Y Z rcons posrecip Y 2ndsneg N Z 2ndsneg 0 Z rnil 2ndsneg s N cons X Z 2ndsneg s N cons2 X Z 2ndsneg s N cons2 X cons Y Z rcons negrecip Y 2ndspos N Z pi X 2ndspos X from 0 plus 0 Y Y plus s X Y s plus X Y times 0 Y 0 times s X Y plus Y times X Y square X times X X 2.2 square X times X X plus s X Y plus X Y pi X 2ndspos X from 0 2ndspos s N cons2 X cons Y Z 2ndsneg N Z 2ndspos s N cons X Z 2ndspos s N cons2 X Z pi X from 0 2ndsneg s N cons2 X cons Y Z 2ndspos N Z times s X Y plus Y times X Y 2ndsneg s N cons X Z 2ndsneg s N cons2 X Z from X from s X times s X Y times X Y true pi X 2ndspos X from 0 false pi X from 0 false from X from s X true Failed! NaTT certifiable-1.6