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1.4 Measuring and Classifying Angles

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Dee Black
Dee Black

The document discusses angles and how to measure them using a protractor. It provides examples of angles in everyday life and notes that the ancient Babylonians were the first to divide a circle into 360 equal parts called degrees. It explains how to properly use a protractor to measure angles, including making sure the protractor is lined up with the vertex of the angle and reading the measurement. The document also classifies different types of angles such as acute, right, obtuse, and straight angles.

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1.4 Measuring and Classifying Angles
Name 3 examples of angles in the real world.
The ancient Babylonians created several systems of measurement. Historians believe that they were the first people to divide a circle into 360 equal parts, called degrees. No matter who invented them, we all use degrees to measure angles.
90属 180属 0属 360属 270属
The symbol for a degree is 属. An angle measurement of 10 degrees is written 10属. To measure an angle you have to use a protractor. A protractor is a tool shaped like half a circle with markings from 0属 to 180属.
You need to make sure the protractor is lined up correctly. Is this ready to measure the angle?
Look for the upside down T in the middle of the straight line on your protractor. This needs to be exactly on the vertex of your angle.
We need to remember..... It doesnt matter which way round the angle is, you ALWAYS need to line the upside down T to the vertex of the angle.
Read from the 0属, and follow the inner set of numbers.
You then need to look at the 1属 markings on the outer set of numbers.
This angle measures 35属.
Turn to page 15 in your textbook. Measure angle a. What did you get?
You can classify an angle using its measure. An acute angle is an angle whose measure is greater than 0 and less than 90属.
1.4 Measuring and Classifying Angles
A right angle is an angle whose measure = 90属.
1.4 Measuring and Classifying Angles
An obtuse angle is an angle whose measure is greater than 90属 and less than 180属.
1.4 Measuring and Classifying Angles
A straight angle is an angle whose measure = 180属.
Look again at the right angles. Lines that form right angles are said to be perpendicular lines. The symbol for perpendicular lines is What 2 lines are perpendicular?
Complete pages 18-19 All You have 15 minutes. Homework: Workbook 5 You need a protractor!!

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1.4 Measuring and Classifying Angles

  • 2. Name 3 examples of angles in the real world.
  • 3. The ancient Babylonians created several systems of measurement. Historians believe that they were the first people to divide a circle into 360 equal parts, called degrees. No matter who invented them, we all use degrees to measure angles.
  • 4. 90属 180属 0属 360属 270属
  • 5. The symbol for a degree is 属. An angle measurement of 10 degrees is written 10属. To measure an angle you have to use a protractor. A protractor is a tool shaped like half a circle with markings from 0属 to 180属.
  • 6. You need to make sure the protractor is lined up correctly. Is this ready to measure the angle?
  • 7. Look for the upside down T in the middle of the straight line on your protractor. This needs to be exactly on the vertex of your angle.
  • 8. We need to remember..... It doesnt matter which way round the angle is, you ALWAYS need to line the upside down T to the vertex of the angle.
  • 9. Read from the 0属, and follow the inner set of numbers.
  • 10. You then need to look at the 1属 markings on the outer set of numbers.
  • 12. Turn to page 15 in your textbook. Measure angle a. What did you get?
  • 13. You can classify an angle using its measure. An acute angle is an angle whose measure is greater than 0 and less than 90属.
  • 15. A right angle is an angle whose measure = 90属.
  • 17. An obtuse angle is an angle whose measure is greater than 90属 and less than 180属.
  • 19. A straight angle is an angle whose measure = 180属.
  • 20. Look again at the right angles. Lines that form right angles are said to be perpendicular lines. The symbol for perpendicular lines is What 2 lines are perpendicular?
  • 21. Complete pages 18-19 All You have 15 minutes. Homework: Workbook 5 You need a protractor!!