year 8 maths

394 Chapter 6 Angle relationships and properties of geometrical figures 1
Angles in a right angle
Angles on a straight line
Angles in a revolution
Chapter summary
a°
25°
a + 25 = 90
a = 65
Vertically opposite angles
a° 40°
a = 40
Triangles
Angle sum = 180°
Scalene
Isosceles
125°
a°
a + 125 = 180
a = 55
Angle relationships and
properties of geometrical figures 1
(2a)°
2a + 240 = 360
2a = 120
a = 60
240°
Parallel lines
• Corresponding angles
are equal (a = b)
• Alternate angles
are equal (a = c)
• Cointerior angles
are supplementary
(a + d = 180)
b° d°
c° a°
100°
35°
a°
a°
50°
a + 135 = 180
a = 45
2a + 50 = 180
2a = 130
a = 65
Exterior angles
c° c = a + b
b°
a°
Quadrilaterals
(square, rectangle, rhombus, parallelogram,
kite, trapezium)
Angle sum = 360°
Non-convex
Parallelogram
40°
a°
a°
240° 70°
35°
120°
b°
b + 300 = 360
b = 60
a = 120
a°
a + 315 = 360
a = 45
a + 70 = 180
a = 110
Symmetry
• 5 lines of symmetry
• Rotational symmetry
of order 5
regular
pentagon
Cambridge Maths NSW
Stage 4 Year 8 Second edition
ISBN 978-1-108-46627-1 © Palmer et al. 2018
Cambridge University Press
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