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What is a reflex angle?

reflex angle
An important geometry concept taught in Key Stage 2 is how to identify different types of angles, including reflex angles. Understanding angles is not just about being able to identify them; it's about recognising their real-world applications, from the hands on a clock to the turning of a wheel.

What is a reflex angle?

A reflex angle is an angle that is greater than 180 degrees but less than 360 degrees. Using an analogue clock can be a really effective visual strategy to help explain this to your child. Ask them to look at a clock face: if you start at 12 and move clockwise all the way to 6, you've just made a half-circle. This is 180 degrees and forms a straight line. Now, if you keep going past 6 and stop somewhere before getting back to 12, you've made a reflex angle!

Here is an example of a reflex angle:

reflex angle

To help explain a reflex angle, it can be useful to compare it to the other angles taught at primary school. These are:

right angleacute angleobtuse angle

When do children learn about reflex angles?

Reflex angles are typically introduced in Key Stage 2, usually towards the end of Year 5 and into Year 6. At this stage, children are learning to identify different types of angles (acute, obtuse, right, straight, and reflex) and to estimate, measure, draw and compare angles.

How can I help my child with reflex angles?

Geometry concepts can be fun to practise with your child and there are lots of ways to help them recognise and draw different angles. Here are a few ways you could help at home:

  • Use a clock: As mentioned above, a clock is a great tool for understanding angles. You can talk about how moving from one number to another creates different angles. For example, moving from 12 to 6 forms a straight angle (180 degrees), but if you keep going to 7, 8, 9, 10, 11 you're forming a reflex angle.
  • Draw angles: Get some paper and a protractor. Draw different types of angles and ask your child to identify which ones are reflex angles. You can also ask them to draw their own reflex angles.
  • Play angle detective: Look for reflex angles in everyday objects around the house or outside. The corner of a book partially opened, a door that's ajar, or the hands on a clock can all form reflex angles.
  • Use digital tools: There are many online games and interactive tools that can help your child practise identifying and working with reflex angles. These can make learning about angles fun and engaging.

Why are reflex angles important?

Geometry is a fundamental area of mathematics that your child will explore throughout their primary education. It's all about shapes, angles, lines, and the space around us. 

It is important to stress to your child that learning key geometry skills and facts not only helps them to understand the world around them but also helps with skills such as measurement, algebra and also spatial reasoning skills.

Identifying and using different angles is a vital part of the maths curriculum especially as children work their way through Year 6. There is often a question in the SATs papers, and it is vital that children are able to spot the difference between these angles. It is also important to remind children that reflex angles are more than just a maths concept – they're a part of the world around us, from the hands on a clock to the opening of a door, reflex angles are everywhere once you start looking for them!

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