Edexcel IGCSE Maths 复习笔记 4.2.1 Angles in Polygons

Edexcel IGCSE Maths 复习笔记 4.2.1 Angles in Polygons

What is a polygon?

  • polygon is a flat (plane) shape with n straight sidesFor example:

    A triangle is a polygon with 3 sidesA quadrilateral polygon with 4 sides

    A pentagon is a polygon with 5 sides

  • In a regular polygon all the sides are the same length and all the angles are the same: 

    A regular polygon with 3 sides is an equilateral triangleA regular polygon with 4 sides is a square

 

 

Working with angles in polygons

1. TOTAL OF INTERIOR ANGLES = 180° × (n – 2)

(because the polygon can be split into n -2 triangles)2. TOTAL OF EXTERIOR ANGLES = 360°

(this exterior angles rule is the same for ANY number of sides!)eg For a hexagon (n=6):

Angles-in-a-Hexagon

a + b + c + d + e + f = 180° × (6 – 2) = 720°

 

p + q + r + s + t + u = 360°

 

 

Interior-Exterior-Angle-for-Regular-PolygonFor REGULAR Polygons:3. EXTERIOR ANGLE = 360 ÷ n4. INTERIOR ANGLE = 180 – Exterior Angle

Exam Tip

Make sure you know whether you are dealing with a regular or irregular polygon before you start a question.

Worked Example

7.2.1-Angles-in-polygons-Worked-Example-1Polygon-Example-REWRITTEN-5-3-20

Worked Example

7.2.1-Angles-in-polygons-Worked-Example-2

转载自savemyexam

更多IGCSE课程
翰林国际教育资讯二维码