# Class 8 Maths Chapter 3 Exercise 3.2 Pdf Notes NCERT Solutions

Class 8 Maths Chapter 3 Understanding quadrilaterals exercise 3.2 pdf notes:-

Exercise 3.2 Class 8 maths Chapter 3 Pdf Notes:-

## Ncert Solution for Class 8 Maths Chapter 3 Understanding quadrilaterals Exercise 3.2 Tips:

Sum of the Measures of the Exterior Angles of a
Polygon

On many occasions a knowledge of exterior angles may throw light on the nature of
interior angles and sides.

TRY THESE

Draw a polygon on the floor, using a piece of chalk.
(In the figure, a pentagon ABCDE is shown).
We want to know the total measure of angles, i.e,
mā 1 + mā 2 + mā 3 + mā 4 + mā 5. Start at A. Walk
along AB. On reaching B, you need to turn through an
angle of mā 1, to walk along BC . When you reach at C,
you need to turn through an angle of mā 2 to walk along
CD. You continue to move in this manner, until you return
to side AB. You would have in fact made one complete turn.
Therefore, mā 1 + mā 2 + mā 3 + mā 4 + mā 5 = 360Ā°
This is true whatever be the number of sides of the polygon.
Therefore, the sum of the measures of the external angles of any polygon is 360Ā°.

Example 1: Find measure x in Fig 3.9.
Solution: x + 90Ā° + 50Ā° + 110Ā° = 360Ā° (Why?)

x + 250Ā° = 360Ā°
x = 110Ā°

Take a regular hexagon

1. What is the sum of the measures of its exterior angles x, y, z, p, q, r?
2. Is x = y = z = p = q = r? Why?
3. What is the measure of each?
(i) exterior angle (ii) interior angle
4. Repeat this activity for the cases of
(i) a regular octagon (ii) a regular 20-gon
Example 2: Find the number of sides of a regular polygon whose each exterior angle
has a measure of 45Ā°.
Solution: Total measure of all exterior angles = 360Ā°
Measure of each exterior angle = 45Ā°
Therefore, the number of exterior angles =
360
45 = 8

The polygon has 8 sides.