{(a+b+c)x(a+b)}*c = { (a+b+c)Xa + (a+b+c)Xb }*c
                            = ( axa + bxa + cxa + axb +bxb + cxb )*c

axa = bxb = 0 (vector)
bxa=-axb

                            = ( cxa +cxb )*c

                            = (cx(a+b))*c

                            = - ((a+b)xc)*c

                            = - (a+b)xcxc

                            according to rules of vector triple product , = - (a+b)X(cxc)

cxc = 0(vector)

ans = 0(vector)