Exterior angles of a polygon

Objectives: To verify that the
sum of measures of the
exterior angles of any
polygon is 3600

Pre-Requisite Knowledge:
Concept of triangles,
quadrilaterals, pentagons
and hexagons

Materials required: Glaze
paper, Geometry box, A pair
of scissors, sketch pens,
fevistick

Preparation for the given
activity: On a glaze paper
make the following figures –
A triangle; A quadrilateral; A
pentagon; A hexagon

Procedure: (i) Extend all the
sides of the above figures to
get the exterior angles of
each figure

Procedure: (ii) A triangle has
three exterior angles (In
figure I)

Procedure: (iii) A
quadrilateral has four
angles (In figure II)

Procedure: (iv) A pentagon
has five exterior angles (In
figure III)

Procedure: (v) A hexagon
has six exterior angles (In
figure IV)

Procedure: (vi) Now cut and
separate angle 1 and angle 2
of the triangle

Procedure: (vii) Join and
paste the cut out pieces of
the angles, vertex to vertex
with angle 3

Procedure: (viii) In the same
way, cut angles a, b and c of
the quadrilateral and
separate them

Procedure: (ix) Join the cut
out pieces vertex to vertex,
the angles to the angles to
the exterior angle d of the
quadrilateral

Procedure: (x) Repeat the
above process with pentagon
and hexagon also. Paste the
out angles to the exterior
angles of the pentagon and
hexagon

Observation: We find that in
each figure, when the angles
are joined to the exterior
angle, we get a complete
angle, that is, an angle of
3600

Result: It is verified that the
sum of measures of the
exterior angles of any
polygon is 3600

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