# Use the terms acute, obtuse and reflex when comparing angles to a right angle

I can use the terms acute, obtuse and reflex when comparing angles to a right angle.

# Use the terms acute, obtuse and reflex when comparing angles to a right angle

I can use the terms acute, obtuse and reflex when comparing angles to a right angle.

## Lesson details

### Key learning points

- Angles are marked with a curve between the lines which have been rotated
- Angles with a bigger turn are larger than those with a smaller turn
- Angles can be bigger than a right ange or smaller than a right angle

### Common misconception

Angles must always be formed with one horizontal line. Angles must also have two straight lines that are exactly the same length.

Provide pupils with examples where acute, obtuse and reflex angles are shown in a wide range of orientations and where the length of the lines leading into the angles differ in size to support generalising the features of each angle type.

### Keywords

Angle - An angle is a measure of turn. It shows how far something has rotated.

Right angle - A right angle is a square corner or a quarter turn.

Acute angle - An angle that is smaller than a right angle is an acute angle.

Obtuse angle - An angle that is greater than a right angle but smaller than a straight line is an obtuse angle.

Reflex angle - An angle that is greater than a straight line up to a full turn is a reflex angle.

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Video

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## Starter quiz

### 6 Questions

A polygon with four equal sides and four right angles.

A polygon with three sides and three vertices.

A polygon with five sides and five vertices.