Shape
Picture
Number of Sides
Interior Angle
Sum of Interior Angles
Exterior Angle
Triangle
3
60
180
120
Square
4
90
360
90
Pentagon
5
108
540
72
Hexagon
6
120
720
60
Octagon
8
135
1080
45
n- agon
O Level Maths Notes: Angles in Polygons
|
Shape |
Picture |
Number of Sides |
Interior Angle |
Sum of Interior Angles |
Exterior Angle |
|
Triangle |
|
3 |
60 |
180 |
120 |
|
Square |
|
4 |
90 |
360 |
90 |
|
Pentagon |
|
5 |
108 |
540 |
72 |
|
Hexagon |
|
6 |
120 |
720 |
60 |
|
Octagon |
|
8 |
135 |
1080 |
45 |
|
n- agon |
|
|
|
|
|
notice
that a triangle has three sides so n=1 and the angles add to 180, a
square can be cut into two triangles, each with internal angles 180,
so all the internal angles of both triangles sum to 360. Consider the
pentagon below. It is cut into three triangle, each with internal
angles that sum to 360, so the internal angles of a pentagon sum to
3*180 =540.