Vertically Opposite Angles
Maths: Year 5 & 6 National Curriculum, topic 8.4.4
Vertically Opposite Angles
Remember that angles around a circle add up to 360° and angles on a straight line add up to 180°. You also need to know about vertically opposite angles.
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Two lines crossing
- Angles that are vertically opposite are made when two lines cross.
- Two lines crossing makes 4 angles.
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Vertically opposite angles
- The angles vertically opposite each other are equal when two lines cross.
- The grey angles are equal.
- The white angles are equal.
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Example question
- You know that one angle is 40°.
- You can work out all the other angles from this.
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Vertically opposite angles
- You know that the angle vertically opposite to the 40° angle will also be 40°.
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Angles around a circle
- You know that the four angles will add up to 360°.
- We have 80° of angles so far (two 40° angles).
- Work out the difference between 360° and 80° to find out what the other two angles add up to.
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Two more missing angles
- You now know the two missing angles add up to 280°.
- The two missing angles will be the same.
- The two missing angles will be the same because they are vertically opposite.
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Two angles are the same
- You can work out the missing angles by dividing 280° by 2 because they are the same.
- Both of the missing angles are 140°.
Test yourself on Vertically Opposite Angles
What is the size of angle a?
What is the size of angle a?
What is the size of angle a?