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AOA; scalar or vector, resolved.
Hi all,
In a tangent many times removed from the original "Who does flight plans?" thread, I became entangled in an argument about whether "AOA was a scalar or a vector". Not finding an adequate resource off-line that clearly resolved the issues involved in assigning either term as a valid math definition, I went to the alt.math newsgroup and posed what I thought was the essence of the problem that lead to my confusion. Thanks to the discussion that followed, I now understand the reason for my confusion over this matter. Anyone interested in the details can find the discussion there. In the end, it was D. Watland's response that provided the clarity that I needed to put this to rest. In our discussion, we were apparently speaking in jargon, not math terms. If we had said, "Angle of Attack is a _variable_ whose value is expressed as a real number...", there would probably have been no argument. My apologies to all whom I said were "wrong" about calling AOA a scalar instead of a vector. Best regards and blue skies! Neil |
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"Neil Gould" wrote in message
.. . In our discussion, we were apparently speaking in jargon, not math terms. No, we were using math terms (and math terms *are* a jargon, i.e., a technical terminology). It's true though that your reference to undefined or null values in the alt.math thread was a mishmash of math jargon and computer jargon, as Watland pointed out. If we had said, "Angle of Attack is a _variable_ whose value is expressed as a real number...", there would probably have been no argument. Since you're interested in the terminology, it should be noted that an angle of attack is *not* a variable, though we can certainly define a variable whose *value* is an angle of attack, which is a real number. For example, we can say "Let x equal the angle of attack of this airfoil...". If an angle of attack were itself a variable, then it would not be correct to say "the angle of attack is five degrees". Instead, we'd have to say "the angle of attack has a value of five degrees". In fact, though, that would be wrong--five degrees *is* the angle of attack. (Similarly, it's correct to say "my height is 1.7m", not "my height has a value of 1.7m".) In the case that you were asking about in the alt.math thread (the case where there is no relative wind), there simply is no angle of attack to be spoken of. It's analogous to vaporizing you in an atomic explosion and asking what your height is *then*. It's just undefined. And that doesn't mean that some "undefined" token is then your height. Rather, it means that there just isn't any number (or any other object) that is then your height. But I'm glad we now agree that AOA is a scalar, even if we don't quite agree on how to reach that conclusion. --Gary |
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