Lines and Angles

Class 7 NCERT and Arjun

• Line segment, ray, line
• angle and its types
  • based on degree
  • based on position - linear, adjacent, vertically opposite
• complementary angles - 90
• supplementary angles - 180
• Pair of lines
  • intersecting lines
  • transversal lines
• Angles made by transversal
  • interior angles
  • exterior angles
  • corresponding angles = equal
  • alternate interior angles = equal
  • sum of interior angles on same side of transversal = 180
    • also known as allied angles or co interior angles or consecutive angles
  • sum of exterior angles on same side of transversal = 180

Class 9 NCERT

• collinear points
• non collinear points
• types of angles
• adjacent and opposite angles
• linear pair of angles
• vertically opposite angles = equal
• sum of adjacent angles = 180
• linear pair axiom - if the sum of 2 adjacent angles is 180, then the non common arms of the angles form a line
• Ex. 6.1
• Pair of lines
  • intersecting lines
  • transversal lines
• Angles made by transversal
  • interior angles
  • exterior angles
  • corresponding angles = equal
  • alternate interior angles = equal
  • interior angles on same side of transversal = 180
    • also known as allied angles or co interior angles or consecutive angles
• Lines which are parallel to same line are parallel to each other
• Ex 6.2
• Angle sum of property of triangles = 180
• If a side of a triangle is produced, then the exterior angle so formed is equal to the sum of the two interior opposite angles
• exterior angle of a triangle is greater than either of its interior opposite angles
• Ex 6.3