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Matrices, TraditionalForm and Two Equal Signs

• To: mathgroup at smc.vnet.net
• Subject: [mg100847] Matrices, TraditionalForm and Two Equal Signs
• From: C Rose <uk.org.microserf at googlemail.com>
• Date: Tue, 16 Jun 2009 21:50:36 -0400 (EDT)

Hi all

I'm trying to display a matrix-vector multiplication in
TraditionalForm. Let A and B be undefined, and let a and b be 2x2 and
2x1 matrices respectively. If I do:

A B == a.b == N[a.b] // TraditionalForm

then I get the product AB, followed by an equality sign, followed by
the resulting 2x1 matrix, but I don't get the following equality sign
and numerical approximation of the dot product.

If I do:

A B == N[a.b] // TraditionalForm

then I do get to see the numerical approximation.

If x and y are undefined and z is set to 1/2, and I do:

x==y==N[z] // TraditionalForm

then I get what I would expect: "x=y=0.333333".

I imagine a call to Hold or similar is the answer, but I'm failing to
find a solution. I'd be very grateful if someone could explain why the
same notation applied to matrices leaves off the rightmost part of the
equation.

Best regards

Chris