~ GCSE Mathematics – Geometry 2 ~
Angles in crossing lines
Use examples from the diagram above to illustrate the following rules:
 Angles on a straight line add up to 180o
 Vertically opposite angles are equal
 Angles at a point add up to 360o
Draw other examples to illustrate these rules.
Angles in triangles and quadrilaterals
Complete the following rules and give examples of each:
 Angles in a triangle add up to _____o
 Base angles of an isosceles triangle are ___________.
 Angles in an equilateral triangle are _________.
 Angles in a quadrilateral add up to _____o
Polygons
 Exterior angles of a polygon add up to _____o
 The interior and exterior angle of a polygon add up to _____o
3
80o
125o
65o
z
45o
33o
130o
y
55o
58o
Cross College GCSE Maths
marian.harrington@abingdon-witney.ac.uk
Regular Polygons
~ GCSE Mathematics – Geometry 2 ~
A regular polygon has sides all of the same length and angles all of the same size.
Number of equal sides
Size of exterior angles
3
4
5
6
7
8
9
10
Size of interior angles
Number of lines of
reflective symmetry
Order of rotational
symmetry
Angles in parallel lines
 Corresponding angles are equal
b
a
c
100
d
26
 Alternate angles are equal
75.5
f
e
g h
i
98
Additional practice: Edexcel 16+ book p. 114 Ex 11A-F
Cross College GCSE Maths
marian.harrington@abingdon-witney.ac.uk