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 3.1

Exercise 3.2 Class 8 maths Chapter 3 Pdf Notes:-

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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.

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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,
m∠1 + m∠2 + m∠3 + m∠4 + m∠5. Start at A. Walk
along AB. On reaching B, you need to turn through an
angle of m∠1, to walk along BC . When you reach at C,
you need to turn through an angle of m∠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, m∠1 + m∠2 + m∠3 + m∠4 + m∠5 = 360°
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 360°.

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

x + 250° = 360°
x = 110°

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 45°.
   Solution: Total measure of all exterior angles = 360°
   Measure of each exterior angle = 45°
   Therefore, the number of exterior angles =
   360
   45 = 8

The polygon has 8 sides.