- Y9 Geometry RulesRule 1: Adjacent angles on a straight lineRule 2: Angles around a pointRule 3: Vertically Opposite AnglesRule 4: Angles in a triangleRule 5: Base angles of isosceles triangleRule 6: Angles of an equilateral triangleRule 7 : Angles in a quadrilateralRule 8: Corresponding Angles on parallel linesRule 9: Alternate Angles on parallel linesRule 10 : Co-interior angles on parallel lines
