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Exploring a Measurement Trail

Some mathematics terms are heard or used so rarely that they seem foreign, even to mathematics teachers.

For example, suppose you overheard someone talking about a quadrantal triangle. At first, this double dose of the prefixes "quad" and "tri" may confuse you. But with a little thought, you might work out that a "quadrantal triangle" is a triangle on a spherical surface with one side equal to an arc of 90o.

But, let me push a little further. What is a "quadrantal," where now the term is being used as a noun rather than an adjective? Surprise, it is a term equivalent to "a cube." Specifically, a quadrantal is a cubical vessel containing exactly one Roman cubic foot, where each side is one Roman square foot.

But you ask, what is a Roman foot? It was equivalent to 16 digits or 4 palms...and was 1/3 of a cubit. Cubits you may have heard of, especially with regard to dimensions of Noah's ark. Also, the ratio of a Roman foot to our English foot is 36:35, just in case you were wondering.