Angles and Properties

Definition An Angle: – Is made when two lines meet at a common end point. The amount of turning needed to make an Angle is given in Degree’s Angle is 35o

Angle Types Acute Angles are between 0o to 90o Obtuse Angles are between 90o to180o Reflex Angles are over 180o A Right Angle equals 90o

Angle Names The angle shown is called either P Q R The angle shown is called either 1) Angle OR 2) Angle OR 3) Angle Note: The middle letter is at the corner or Vertex of the angle.

Look at each of these angles. Practice Look at each of these angles. Decide if each is A acute, O obtuse or R right-angled. 1 2 A O 3 5 4 A R R 6 7 A A O 8

Use the letters to name these angles Practice Use the letters to name these angles 1 P T C 2 D R B

1 2 3 4 5 6 7 8 9 Acute Acute Obtuse Right Obtuse Reflex Obtuse Acute

Measuring Angles

What do we use to help us? A protractor Here is a standard protractor like you use in the classroom.

When we use a protractor, we need to line it up correctly. 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 corner or vertex of your angle.

We need to remember..... It doesn’t 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°, and follow the inner set of numbers.

Once you reach 30° you need to be careful!!! You then need to look at the 1° markings on the outer set of numbers.

What does it measure? This angle measures 35°.

Using a Protractor 1 50o 2 67o 0 on the inside so use inside scale 0 on the outside so use outside scale

Drawing Angles

Step One Get a protractor

Step Two Put 3 dots

Step Three Move the Protractor

Step Four Get a ruler

Step Five Draw a line along the bottom

Step Six Draw a line along the side

Step Seven Draw a curved arc between the lines

Angles Properties Some angles can be worked out without measuring 1) Angles on a straight line add up to 180o a + b = 180o a b E.G a + 50o = 180o a = 130o a 50o

Angles around a point add up to 360o 2) Angles around a point add up to 360o E.G a a a + 90 + 120o = 360o a = 150o b 90 c 120 a + b + c = 360o 3) Vertically opposite Angles are equal E.G a b a 80o a = 80o ao = bo