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# Interior & Exterior Angles

lesson going over interior and exterior angles for KS3 and KS4
by

## Rob Graham

on 27 September 2012

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#### Transcript of Interior & Exterior Angles

Exterior and Interior Angles of Regular Polygons All students will be able to calculate the Exterior Angle of a Regular Polygon given the number of sides.

Most will be able to calculate the Interior Angles of a Regular Polygon.

Some will be able calculate the
Sum of Interior Angles. Success Criteria All the exterior angles of a Polygon add up to 360 degrees.

The Interior and Exterior Angles add to 180 degrees.

Also number of triangles
method. How are we going to Calculate these Angles? To understand how to calculate
the Exterior Angles of a Polygon.

Using Exterior Angles, be able to calculate the Interior Angle of a Polygon. Learning Objectives Can you tell me what is a Regular Polygon?

Can anyone guess what is an
Irregular Polygon? What Is A Regular Polygon? What information do we need to find
the Exterior Angles of a Regular Polygon?

How do we calculate the Exterior Angles?

How do we calculate the Interior Angles of the Polygon?

What is a Regular and Irregular
Polygon? To Summarise... Polygon comes from Greek.
Poly- means "many" and -gon means "angle".

A polygon is a two dimensional shape; they are made of
straight lines and the shape is "closed".

There are two types of polygon, regular and irregular. Regular
Octagon Regular
Heptagon Regular
Hexagon Regular
Pentagon Square Equilateral
Triangle
In a regular polygon all lengths and angles are the same size. In an irregular polygon all lengths and angles are different sizes. a + b + c
=
180 degrees! What do angles in a triangle add up to? b c a 360 ÷ 4 = 90°

We can divide a square into two triangles

Two triangles in a square gives a total of:
2 × 180 = 360°
Size of one interior angle is: 90° 90° 90° 90° 540 ÷ 5 = 108°
We can divide a pentagon into three triangles

Three triangles in a pentagon gives a total of:
3 × 180 = 540°
Size of one interior angle is: 108° 108° 108° 108° 108°
Full transcript