If a,b,c areunit vectors and a+b+c=i+j-2k,then a.b+b.c+c.a=

Dear pallavi

a+b+c=i+j-2k

|a+b+c|²=|i+j-2k|²

|a|²  +|b|²  +|c|²     +2(a.b +b.c+c.a)  =6

 2(a.b +b.c+c.a)  =6 -3 =3

(a.b +b.c+c.a)  =3/2

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