1. The problem statement, all variables and given/known data Prove that (A X B) X C = AxBxCx (i x k) + AyBxCy (j x k) where i , j and k are unit vectors ? 2. Relevant equations 3. The attempt at a solution let A= Axi+Ayj B= Bxi+Byj L.H.S = (AXB)XC = (C.A) B - (C.B) A = (AxCx+AyCy)(Bxi+Byj)- (BxCx+ByCy)(Axi+Ayj) after simplification we get = AxByCx i - AxByCy j + AyBxCy i - AyBxCx j there i am held up.... now how i proceed further..