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SOLVED

## Re: Units in roman

To complete the answer to Philips question.

Opposed to empirical equations (or relationships) you have theoretical equations, those that are derived from knowledge, things that are known (or sometimes postulated) to be true. Such relationships often are fundamental laws.

And in between you might consider approximations.

Luc

## Re: Units in roman

 Richard Jackson wrote: Yep.  That saves me from some typing. Is your answer to me any shorter than the one to Philip would have been?

Indubitably, my dear Jackson.  For why use 1 word where 30 will suffice?

Stuart

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## Re: Units in roman

 LucMeekes wrote: To complete the answer to Philips question. Opposed to empirical equations (or relationships) you have theoretical equations, those that are derived from knowledge, things that are known (or sometimes postulated) to be true. Such relationships often are fundamental laws. And in between you might consider approximations.

An interesting rule; unfortunately most examples don't appear to follow it. Most do have theory behind them. Re: Dimensional Constants in Valve Sizing Equations? is the current example.

To me it's as if it's also the distinction is between coherent (BIPM - coherent units) and incoherent units (Coherence (units of measurement) - Wikipedia, the free encyclopedia), and also those that are simplifications (which hide the theory), and are usually recognisable by the need to convert measurement values into local customary units for the purpose of evaluating the arithmetic equation. The mathematicians sin() would appear to fall into the latter, given they have no dimensions at all;-)

## Re: Units in roman

 An interesting rule; unfortunately most examples don't appear to follow it.

All examples follow it, because it's not a rule, it's a definition. Empirical equations are not based on any fundamental theory. The units may or may not work in such an equation, but usually they don't. If the units in a theoretical equation don't work out then the theory was wrong.