Dictionary.com
definitions

supplementary angle

noun Mathematics.
  1. either of two angles that added together produce an angle of 180°.
Compare complementary angle.

Origin of supplementary angle

First recorded in 1830–40
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
British Dictionary definitions for supplementary angles

supplementary angle

noun
  1. either of two angles whose sum is 180°Compare complementary angle
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
supplementary angles in Science

supplementary angles

[sŭp′lə-mĕn′tə-rē]
  1. Two angles whose sum is 180°.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.