Vector multiplication??

*To*: mathgroup at yoda.physics.unc.edu*Subject*: Vector multiplication??*From*: "Katherine (Williams) Derbyshire" <kewms at kew.com>*Date*: Sun, 29 Nov 1992 15:48:41 EST

I have an arbitrary vector A = Array[a,3] = {a[1], a[2], a[3]} The dot product of this vector with itself, is evaluated correctly by Mathematica: a[1]^2 + a[2]^2 + a[3]^2 The 'ordinary' product of this vector with itself, A^2, should be equivalent to the dot product. It is, in fact, conventional in mechanical engineering to interpret A^2 as the square of the magnitude of A, (i. e. as a dot product). My linear algebra text doesn't offer any definition for this expression at all. Unfortunately, Mathematica (2.0 for Windows) interprets A^2 as {a[1]^2, a[2]^2, a[3]^2} which isn't the same at all. What's going on here? I know I could fix this by writing a transformation rule, but it would be nice if Mathematica didn't give wrong answers in the first place. -- Katherine (Williams) Derbyshire kewms at kew.com Are we having fun, yet?