1.( 1)x x 140 90 =(4-2)* 180 x = 65

(2) 120 150 90 2x =(5-2)* 180 x = 60

P84 exercise

(3) 120 80 75( 180 x)=(4-2)* 180 x = 95

(4) Because AB is parallel to CD.

So ∠ b ∠ c = 180.

So ∠ b = 180-60 = 120.

x 150 60 135 120 =(5-2)* 180 x = 75

2.6

3.4

Exercise 7.3

1.

2.( 1)540 -60 =4x x = 120

(2)3x 4x 3x 2x =(4-2)* 180 x =30

3. Sum of internal angles:180 360 540 72010801800.

Sum of external angles: 360 360 360 360 360 360 360 360 360 360 360.

4. Regular pentagon: 108 Regular decagon: 144.

5.9

6.( 1)3

(2)6

7.∠∠A∠B∠C∠D = 360

∠A =∠c∠B =∠D

∫2∠a2∠D = 360

∴∠A ∠D= 1/2*360 = 180

Ab parallel CD

BC parallel AD

8.( 1) Based on BD, the CO is high.

(2)30

(3)D = 60 45 = 105

∠C = 90°

∠=30 *2=60

∞= B = 105

9.∵ Pentagon ABCD are all equal

∴∠e=[(5-2)* 180]/5 = 108

∴∠ 1=∠2=( 180 - 108 )/2=36

∴∠3=∠4=36

∴X= 108-(∠ 1 ∠3)=36

10.AB parallel DE BC parallel EF

∫ The inner angles of hexagonal ABCDEF are all equal.

∴∠b=[(6-2)* 180]/6 = 120

∫∠ Bad =60

∴∠b∠ bud = 180

BC parallel AD

∫∠DAF = 120-60 = 60

∴∠F ∠DAF= 180

Ef parallel advertisement

Bc parallel EF