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Angles and Lines

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.

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Angles and Lines

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  1. Angles and Lines Slideshow 36, Mathematics Mr Richard Sasaki, Room 307

  2. Review angle properties learned so far • Understand alternate angles • Calculate missing angles at certain points Objectives

  3. Let’s have a look back at what we have learned so far. Angle Properties • A polygon with n sides has a sum of interior angles ___________. 180(n-2)o • Any polygon has sum of exterior angles ________. 360o • At a point, a polygon’s interior and exterior angle add up to ________. 180o

  4. Angle Properties 90o • A right-angle is exactly _______. • On an Equilateral triangle, each angle is ______. 60o • On two straight lines, opposite angles are always ________. equal

  5. Try the first worksheet! Angle Properties A pair of parallel lines have two corresponding angles between them that add up to _______. 180o All angles around a point add up to _______. 360o

  6. 1 • b. • c. • d. • e. • f. • 2. Answers • 1 • b. • c. • d. • e. • f. • 2. 72o • 3.

  7. Alternate Angles • You 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.

  8. Naming Lines and Angles • Lines are often labelled and this gives the ability to name angles. E • A B Angle can be known as AEF or FEA. D C 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.

  9. Let’s try the Activote exercise. Line Segments • Shapes are usually made of line segments. B • A Here, AB, AC, CD and BD are line segments. C D Which two line segments are parallel? AB and CD We can denote this as AB CD. (“” means parallel.)

  10. Try the final worksheet! 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

  11. Answers • Acute, obtuse, right-angle Acute, straight, reflex Reflex, acute, right-angle 2. Reflex 3. It must be acute, a right angle or obtuse 4. 4 5. AB CD, (or 6. Line, line segment

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