Watch: Different types of angles
Watch this video to learn about acute, obtuse, right and reflex angles.
Types of angles
An angle is the space between two lines that start at the same point and you measure them in degrees.
Angles can be between 0掳 and 360掳.
A right angle looks like the corner of a square or the edge of a book.
It is a perfect 90掳, which is often shown by a small square drawn in between the two lines.
An acute angle is an angles that is less than 90掳. This makes them smaller than a right angle.
An obtuse angle is an angle that is bigger than 90掳 degrees, but doesn鈥檛 reach a straight line at 180掳.
A reflex angle is an angle that is greater than 180掳.
Example 1
You can measure an angle using a protractor. Let's look at how you do this鈥
Step 1: Line up the vertex (corner) of the angle with the cross section of the protractor.
Step 2: Make sure that one of the angle lines goes right through the zero.
Remember
These steps are really important - if the protractor isn鈥檛 lined up properly with the angle, you won鈥檛 get a correct reading.
Step 3: See which number the other line of the angle reaches on the protractor.
Step 4: Take your measurement.
The line goes through both 120掳 and 60掳. Always read from the zero. Since the zero is on the inside line, you continue to read the inside numbers - the angle must be 60掳.
You can also tell that the angle is an acute angle so it has to be less than 90掳.
Example 2
Use the protractor to measure this angle. The protractor has already been lined up correctly.
Look for the zero line that the angle line goes through. It is on the inside so you have to read the inside numbers.
The other angle line is in directly between two numbers - 130掳 and 140掳.
The angle measures 135掳.
Always check which two numbers the angle is in between and remember the direction the numbers are going in.
It is easy to make a mistake and write 145掳 instead.
Example 3
Use the protractor to measure this angle. The protractor has already been lined up correctly.
The zero line is on the left this time, so you need to read the outside numbers.
The other angle line goes directly through 70掳 and 110掳.
The angle must be 70掳 degrees since it is the outside number.
Activities
Activity 1
Label the angles
Can you identify and label the angles correctly in this KS2 Maths interactive activity?
Activity 2
Angle Hunt
Angles are everywhere! Armed with your knowledge of acute , obtuse, reflex and right angles, go on a hunt around your house, garden or even whilst out on a walk and see what angles you can see.
Can you spot at least five examples of each type of angle?
You may wish to record you findings in a table like the one below or take a photo.
acute | obtuse | reflex | right - angle |
---|---|---|---|
Corner of a window | |||
Extension challenge
Have a go at measuring some of the angles you find with a protractor!
Quiz
NEW! Play Guardians: Defenders of Mathematica - the Halloween update. gameNEW! Play Guardians: Defenders of Mathematica - the Halloween update
Experience Mathematica as you鈥檝e never seen it before, with all-new backgrounds and costumes for Halloween. Available for a limited time only. Use your maths skills to save the day before it's too late!
More on Lines and angles
Find out more by working through a topic
- count5 of 10
- count6 of 10
- count7 of 10
- count8 of 10