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perpendicular: At right angles to plane of horizon. So 'perpendicular' means 'vertical'. I always thought it meant at right angles to anything ;-) It seems that others are confused too: http://dictionary.reference.com/search?q=right%20angle "An angle formed by the perpendicular intersection of two straight lines; an angle of 90°. However.. http://thesaurus.reference.com/search?q=perpendicular Synonym: vertical (Alan: no mention of 90 degrees) Antonym: horizontal We are incorrect in saying that vertical (or perpendicular) means at right angles to. Vertical (or perpendicular) is DEFINED as being at right angles to plane of horizon (ONLY AT RIGHT ANGLES TO PLANE OF HORIZON) not at right angles to anything we choose. Quote:
Of all the myriad of possible planes, Vertical and Horizontal planes are special, absolute, cases (defined by Man), as all other (angled) planes fall within these two limits. 'Horizontal', 'Vertical' and 'Angled' are all adjectives but the first two are also nouns e.g. "..to the Vertical" Quote:
No wonder I couldn't understand some of the text! |
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http://dictionary.reference.com/search?q=perpendicular 1. Mathematics. Intersecting at or forming right angles. 2. Being at right angles to the horizontal; vertical. See Synonyms at vertical. In message <123j0rlfss99o9f@news.supernews.com>, Alan Illeman <illemann@surfbest.net> writes >I'm studying a book about geometry (of the golf swing) where the >author describes something being vertical to an angled plane, >when he really means, IMO, "at right angles to" an angled plane. > >I always thought that "vertical" and "horizontal" were absolutes >(it's either vertical or it isn't) carved in stone, and that all angled >planes fall between these two fixed limits. They are almost absolute, but approximations are allowed. > >I sought confirmation from my Concise Oxford Dictionary (1968) > >(1)HORIZONTAL: Of, at, the horizon; parallel to a plane of this; at > right angles to the vertical. >(2)VERTICAL: Perpendicular to plane of horizon. >(3)PERPENDICULAR: At right angles to plane of horizon. Not necessarily; this is the original meaning, but perpendicular can always be qualified by reference to a different plane or line. >(4)RIGHT: (of angle) neither acute nor obtuse, of 90 degrees, made > by lines meeting not obliquely but perpendicularly. > >I'm amazed that COD confuses me even more. > >http://dictionary.reference.com/search?q=perpendicular >1. Mathematics. Intersecting at or forming right angles. >2. Being at right angles to the horizontal; vertical. See Synonyms at > vertical. > >If the context is in doubt, how do I decide which of these two >meanings is appropriate? The context should always make it clear whether the word is being used in an absolute sense, or relatively. If no relative is specified, take it as absolute, meaning vertical or upright. -- |
Vertical -- Absolute And Relative
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I applaud your research and the intellectual curiosity that inspired it. You are on the right track here. In TGM, as a Basic Plane of Motion, the term Vertical is used in an absolute sense. As a geometrical alignment, it is used in a relative sense, i.e., defining a right angled relationship to any one of the Three Basic Planes -- Horizontal, Angled or Vertical. |
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