1 General Mental and Psychological Abilities · 1.4.2 Geometry and trigonometry

1.4.2.2 Triangles: angle properties, congruence, similarity and centres

Triangle questions use the 180° angle sum and the exterior-angle rule for angles, the triangle inequality for sides, ratios for similar figures, and four centres whose angle formulas (90 + A/2, 2A, 180 − A) answer most "find ∠BOC" questions.

  • APPSC Group 1
  • Advanced level
  • 7 min read
  • Full course

Key terms

  • angle sum
  • exterior angle
  • triangle inequality
  • congruence
  • SSS
  • SAS
  • ASA
  • RHS
  • similarity
  • basic proportionality theorem
  • angle bisector theorem
  • mid-point theorem
  • centroid
  • incentre
  • circumcentre
  • orthocentre
  • median
  • Apollonius

What this note covers

  1. Core factsFoundation
  2. ExplainedStandard
  3. DeeperAdvanced
  4. Common trapsFoundation
  5. Quick revisionFoundation

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