So I have this small problem. Two vectorsAandBadded together give the vectorS. Show that S (which I'm assuming is the scalar ofS) is equal to (A^2 + B^2 + 2AB Cos (theta) ) / 2 remembering thatS. S =S^2 andS= A+B.I'm really not sure how to make a start on it. I'm thinking that it has something to do with the rulea.b= [a][b]cos theta, but I can't seem to make the first leap. Any suggestions