Changes

Introduce a suitably generic definition of the extended universe of discourse:

Introduce a suitably generic definition of the extended universe of discourse:

Let <math>U = X_1 \times \ldots \times X_k</math> and <math>\operatorname{E}U = U \times \operatorname{d}U = X_1 \times \ldots \times X_k \times \operatorname{d}X_1 \times \ldots \times \operatorname{d}X_k.</math>

<math>\begin{array}{ccclll}

\text{Let}  & U

& = &

X_1 \times \ldots \times X_k.

\text{Then} & \operatorname{E}U

& = &

X_1 \times \ldots \times X_k ~\times~ \operatorname{d}X_1 \times \ldots \times \operatorname{d}X_k

U \times \operatorname{d}U.

\end{array}</math>

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<pre>