GCSE Maths (Edexcel)

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Allied Angles

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Geometry and Measures Properties and Constructions

Allied Angles

3:43 Angles Around Parallel Lines
Spec G3
Previous Alternate Angles Next Interior Angles in a Triangle
  • Allied angles are formed when two lines are crossed by a transversal line
  • Allied angles are on the same side of the transversal and inside the two lines
  • Allied angles can be recognized by a C shape or a backward C shape formed by the three lines
  • When two lines crossed by a transversal are parallel, the allied angles add up to 180 degrees
  • Lines are parallel if they travel in the same direction and never meet even when extended to infinity
  • In the example given, angle X is 60 degrees because it is the missing angle that, when added to the given angle of 120 degrees, equals 180 degrees

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