ObjectiveTo find missing angles using rules of geometry.

1
Objective-To find missing angles using rules of
geometry.
Supplementary Angles-
Angles whose sum is 180 .
a
b
2
Find the value of x.
x
30
x 30 180
- 30 - 30
x 150
3
Find the supplement of the given angle.
1) 40
5) 89
140
91
2) 18
162
6) 23
157
3) 153
27
7) 131
49
4) 65
115
8) 118
62
4
Write a variable equation and solve.
Find an angle whose supplement is 30 less than
twice the angle.
x
2x - 30
x (2x - 30) 180
3x - 30 180
30 30
3x 210
70
x 70
5
Complementary Angles
- Angles whose sum is 90 .
b
a
x 40 90
- 40 -40
x
40
x 50
6
Find the complement of...
1) 20
70
2) 47
43
No complement
3) 100
4) the supplement of 150
the complement of the supplement of 150
30
the complement of
60
7
Write a variable equation and solve.
Find an angle whose complement is 20 more than
three times the angle.
x 3x 20 90
x
4x 20 90
3x 20
- 20 -20
4x 70
4 4
x 17.5
8
- the sum of the interior angles of any triangle
is always 180 .
180 Rule for Triangles
b
80
x
40
a
c
40 80 x 180
120 x 180
x 60
9
Find each angle below.
y 14 63
2y - 10
2y - 10 88
y - 20 29
y14
y - 20
180
(y 14) (2y - 10) (y - 20) 180
4y - 16 180
16 16
4y 196
y 49
10
Vertical Angles Theorem
- the opposite angles of intersecting lines must
be equal.
11
Vertical Angles Theorem
- the opposite angles of intersecting lines must
be equal.
12
Vertical Angles Theorem
- the opposite angles of intersecting lines must
be equal.
Find the missing angles a, b and c.
25
155
b
c
a
25
13
Vertical Angles Theorem
- the opposite angles of intersecting lines must
be equal.
Find the missing angles a, b and c.
25
155
b
c
a
155
25
14
Find the missing angle.
x
40
132
15
Find the missing angle.
119
124
x