Question

find the angle between A vector -B vector(a-b) and A vector multiply B vector(a*b)

Answer 1

Plus or minus the square root of the B vector squared minus 4 times the A vector dot product with the C vector divided by the magnitude of 2 times the A vector

Answer 2

It doesn't make any sense to multiply vectors, unless you are talking about the dot product... and the result is not a vector so it can't form an angle.