Mathcad Definition and 51 Threads

How can you define a four vector in mathcad? Bascially, I want to adjust the vector (mutiplying by arbitary constants if necessary): I = \left(\begin{array}{c}cdt\\dx\\dy\\dz\end{array}\right) such that: |I|^2 = c^2dt^2 - dx^2 - dy^2 - dz^2