If the four vectors a,b,c,d are coplanar, then `(a xx b) xx (c xx d)` =

If a,b,c,d are four vectors then (A xx b) xx (C xx d) =

If the vectors vec a, vec b, vec c are coplanar then (vec a xx vec b)* vec c = (vec b xx vec c)*vec a =...........

If four vectors bar(a),bar(b),bar(c),bar(d) are coplanar,then (bar(a)xxbar(b))xx(bar(c)xxbar(d))=

If a,b,c are the position vectors of A,B,C of Delta ABC then (a xx b) + (b xx c) + (c xx a) =