Quandaries and Queries



I am a maths teacher at a secondary school in Australia. I was hoping you could clear up a question that a fellow teacher and I disagree about!

Is the term supplementary angles only applicable to 2 angles (ie. a pair of angles) or can it be used when talking about 3 or more angles that add to make 180 degrees?





Hi Rosemary,

I checked four sources.

  1. I asked Chris who is my "geometry expert" and he said that supplementary only applies to two angles but that I should check the Oxford English Dictionary.
  2. I checked the online Oxford English Dictionary and there, the pertimant part of the definition of supplement is "(b) supplement of an arc or angle, the amount by which an arc is less than a semicircle, or an angle less than two right angles; also attrib., as supplement-chord."
  3. I wnnt to Earliest Known Uses of Some of the Words of Mathematics and the use there is also for two angles only.
  4.  I went to the Interactive Mathematics Dictionary and found
    Supplementary Angles:  Supplementary angles are two angles whose sum is 180 degrees.

My conclusion is that supplementary is only applicable to two angles.



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