IGCSE›Cambridge IGCSE Maths›Mind mapsAngles in Polygons & Parallel LinesCambridge IGCSE Maths: Mind mapStudy pack PDFAlso for this subtopic:Revision notesFlashcardsSubtopic testCover factsBasic factsAngles at a point sum to 360°Angles on a straight line sum to 180°Vertically opposite angles are equalTriangle sums to 180°, quadrilateral 360°Parallel linesCorresponding angles equal (F pattern)Alternate angles equal (Z pattern)Co-interior angles sum to 180° (C pattern)PolygonsInterior angle sum: (n−2)×180°(n-2)\times180°(n−2)×180°Exterior angles sum to 360°Regular: each exterior =360°n=\frac{360°}{n}=n360°Interior + exterior === 180°Angle rulespolygons, parallels180°360°Worked exampleRegular hexagon, n=6n=6n=6Exterior =3606==\frac{360}{6}==6360= 60°Interior =180−60==180-60==180−60= 120°Giving reasonsAngle ABCABCABC has its vertex at BState the value, then the reasonName the rule, not just the calculationExam tipsSubtract 2 from nnn before multiplying by 180°Use correct terminology for the reason mark