Presentation on theme: "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."— Presentation transcript:
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 35 o
Angle Types Acute Angles are between 0 o to 90 o Obtuse Angles are between 90 o to180 o Reflex Angles are over 180 o A Right Angle equals 90 o
Angle Names P Q R The angle shown is called either 1) Angle 2) Angle OR 3) Angle OR Note: The middle letter is at the corner or Vertex of the angle.
Look at each of these angles. Decide if each is A acute, O obtuse or R right-angled Practice A O R A R O AA
Use the letters to name these angles 1 P T R 2 C B D
Acute Obtuse Acute Reflex Right Obtuse Acute Reflex Obtuse
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°.
1 2 Using a Protractor 0 on the outside so use outside scale 0 on the inside so use inside scale 67 o 50 o
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 180 o a b a + b = 180 o E.G a 50 o a + 50 o = 180 o a = 130 o
2) Angles around a point add up to 360 o a b a + b + c = 360 o E.G a o = 360 o a = 150 o c a ) Vertically opposite Angles are equal a b a o = b o E.G a 80 o a = 80 o