angles and lines
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Angles and Lines. Slideshow 36, Mathematics Mr Richard Sasaki, Room 307. Review angle properties learned so far Understand alternate angles Calculate missing angles at certain points. Objectives. Let’s have a look back at what we have learned so far. Angle Properties. - PowerPoint PPT PresentationTRANSCRIPT
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Angles and Lines
Slideshow 36, Mathematics
Mr Richard Sasaki, Room 307
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Objectives
Review angle properties learned so farUnderstand alternate anglesCalculate missing angles at certain points
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Angle PropertiesLet’s have a look back at what we have learned so far.
A polygon with n sides has a sum of interior angles ___________.
Any polygon has sum of exterior angles ________.
180(n-2)o
360o
At a point, a polygon’s interior and exterior angle add up to ________.180o
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Angle Properties
A right-angle is exactly _______.90o
On an Equilateral triangle, each angle is ______.60o
On two straight lines, opposite angles are always ________.equal
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Angle Properties
𝑥180𝑜−𝑥
A pair of parallel lines have two corresponding angles between them that add up to _______.180o
𝑥360𝑜−𝑥
All angles around a point add up to _______.360o
Try the first worksheet!
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Answers1. 1
2. b.
3. c.
4. d.
5. e.
6. f.
7. 2. 72o
8. 3.
1. 1
2. b.
3. c.
4. d.
5. e.
6. f.
7. 2.
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Alternate AnglesYou should have found out from the last question on the worksheet that o and e are the same size.
e
o
These are called alternate angles and are shaped in like a “Z” format where the top and bottom lines are parallel.
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Naming Lines and Angles
Lines are often labelled and this gives the ability to name angles.
A B
C D
E
F
Here we can see lines AB, CD and EF. (Note: Line AB and BA are the same.)
Lines are of infinite length. Lines that aren’t are called line segments.
𝑥Angle can be known as AEF or FEA.
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Line SegmentsShapes are usually made of line segments.
A B
C D
Here, AB, AC, CD and BD are line segments.
Which two line segments are parallel?
AB and CD
We can denote this as AB CD.
(“” means parallel.)
Let’s try the Activote exercise.
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Acute, Obtuse or Reflex?We know that a right-angle is 90o, there is 180o on a line and 360o around a point but how about in between?
Between 00 and 90o Acute
Between 900 and 180o
Obtuse
Between 1800 and 360o Reflex
Try the final worksheet!
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Answers 1. Acute, obtuse, right-angleAcute, straight, reflexReflex, acute, right-angle2. Reflex3. It must be acute, a right angle or obtuse4. 45. AB CD, (or
6. Line, line segment
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