(related to Proposition: Multiplication of Real Numbers Is Associative)
Multiplying more than two numbers can be defined as a repeated multiplication of two numbers, using a suitable parenthesization:
\[\prod_{i=1}^n x_i=x_1\cdot x_2\cdot x_3\cdot\ldots\cdot x_n:=(\ldots((x_1\cdot x_2)\cdot x_3)\cdot\ldots\cdot x_n\]
Proofs: 1