# MathCAD help! Multiplying matrices with variables.

## Main Question or Discussion Point

I am fairly novice user of MathCAD. I am using version 14. I am trying to multiply a diagonalized 3x3 matrix containing only variables with another matrix completely populated with numbers and no variables. However, when I create the 3x3 matrix with only variables, the variables are highlighted and MathCAD tells me “the variable is undefined”. I am hoping to multiply these to matrices and have a result with the variables multiplied by constants. I know this can easily be done by hand, but I would like to learn how to do this with MathCAD so I can be prepared when I have to multiply larger matrices in the future. Any thoughts?

## Answers and Replies

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First define your variables one by one then later put them into the matrix

Is there a way to do it without defining the variables? I would like a solution that contains the variables in it, and if I define the variables beforehand, then they are eliminated in the operation.

I don't get your question exactly and I don't use MathCAD but it is a common mistake. what I mean is define a b c d as symblolic variable. Then A = [a b;c d].

Bump for any help. Thanks!

Any ideas?!?

Hepth
Gold Member