POLYGONS AND QUADRILATERALS

• Polygon


  A closed figure made up of three or more line segments joined at their endpoints
• Polygon


  The term came from the Greek words 'poly' and 'gonia' meaning 'many angles'
• Polygon


  • Each side intersects exactly two other sides, one at each endpoint
  • No two sides with a common endpoint are collinear
• Regular polygon


  A polygon with congruent sides and congruent angles
• Convex polygon


  A polygon that determines a convex region, where none of the vertices are pointed inward
• Concave polygon


  A polygon that determines a concave region, with at least one interior angle greater than 180 degrees
• Regular convex polygon


  All sides are congruent and all angles are congruent
• Equilateral polygon


  All sides are congruent
• Equiangular polygon


  All angles are congruent
• Quadrilateral


  A polygon with four sides, four angles, and four vertices
• Quadrilateral


  The word is derived from the Latin words 'quadri' (four) and 'latus' (side)
• Quadrilateral


  • Has four sides: AB, BC, CD, and DA
  • Has four vertices: Points A, B, C, and D
  • Has four angles: ∠ABC, ∠BCD, ∠CDA, and ∠DAB
  • ∠A and ∠B are adjacent angles
  • ∠A and ∠C are the opposite angles
  • AB and CD are the opposite sides
  • AB and BC are the adjacent sides
• Types of Quadrilaterals


  • Trapezium (one pair of parallel sides)
  • Parallelogram (both pairs of opposite sides are parallel)
  • Rectangle (parallelogram with four right angles)
  • Rhombus (parallelogram with four congruent sides)
  • Square (parallelogram with four congruent sides and four right angles)
  • Kite (two pairs of adjacent sides congruent and no opposite sides congruent)