Triangles

Triangle side and angle constraints are linked, and special triangles gain additional consequences from equality and symmetry.

What you'll learn

  • Use the 180° triangle angle sum in a specifically identified triangle.
  • Infer equal opposite angles from equal sides and equal opposite sides from equal angles.
  • Classify triangles by stated properties rather than orientation.
  • Derive an exterior angle through triangle sum and a straight-line supplement.
  • Enumerate all possible angle roles in an isosceles triangle without overlap.

Before you start

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