1. d = 180°-120°= 60°
(∠s on a straight line)
= 130°
f = 180°-130° = 50°
(∠s in a triangle)

2. (vertically opposite ∠s)
= 115°
t = 180°-115° = 65°
(∠s in a triangle)

3. (∠s in an isosceles triangle)
= 140°
𝒙 = 140°÷ 2 = 70°
(∠s in an isosceles triangle)

4. (∠s in a quadrilateral) (∠s in a quadrilateral)
= 280°
= 310°
d = 360°- 310°
d = 360°- 280°
d = 80°
d = 50°
(∠s in a quadrilateral)
(∠s in a quadrilateral)

5. (∠s in a quadrilateral ) (∠s in a quadrilateral )
= 320°
= 300°
d = 360°- 300°
d = 360°- 320°
d = 40°
d = 60°
(∠s in a quadrilateral )
(∠s in a quadrilateral )

6. (∠s in a quadrilateral) (∠s in a quadrilateral)
= 140°
360°- 140° = 220°
2d= 220°
d= 220° ÷ 2 = 110°
(∠s in a quadrilateral)
= 230°
360°- 230° = 130°
2d= 130°
d= 130° ÷ 2 = 65°
(∠s in a quadrilateral)

7. ANGLE FACTS 7

8. Calculating missing angles
9/12/2018
Calculating missing angles
180°
Angles on a straight line add up to 180°
Angles in a triangle add up to 180°
360°
Angles in a full turn add up to 360°
Angles in a quadrilateral add up to 360°
Intersecting Lines
Opposite angles are equal
The angles add up to 360°

9. EXAMPLES Work out the missing angles below: 1) 2) 3) 4) 5) 6) 7) 8)
150° 1)
120° 2) c 3) 4)
130°
60°
30° b
30° d
50°
90° e
30° a
120°
Vertically opposite angles are equal
Vertically opposite angles are equal
Angles on a straight line add to 180°
Angles on a straight line add to 180°
Angles on a straight line add to 180° 5) 6) 7) 8)
97°
75°
130°
121° k
130°
110° f
40°
102°
70° h g
78° i j
52°
62°
85°
90°
120°
52°
Angles around point add to 360°
Angles in a triangle add to 180°
Angles in a quadrilateral add to 360°
Vertically opposite angles are equal
Angles on a straight line add to 180°
Angles in a quadrilateral add to 360° 9

10. Find the Missing Angles10

11. How well do you understand the objective?.
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