Geometry and measuresKey Stage 3

Angles in a trapezium

Use parallel sides and recognise the extra isosceles property.

  • Angles along the same non-parallel side add to .
  • An ordinary trapezium does not have to have equal base angles.
  • An isosceles trapezium has equal non-parallel sides and equal base angles.

Example 1

Find angle in the trapezium.

The top and bottom are parallel, so these two angles add to 180°.

Example 2

Find angle in the isosceles trapezium.

The base angles are equal because the trapezium is isosceles.Angles along the same non-parallel side add to 180°.

Your turn

Question 1

Find angle in the trapezium.

Check answer
The top and bottom are parallel, so these two angles add to 180°.
Question 2

Find angle in the isosceles trapezium.

Check answer
The base angles are equal because the trapezium is isosceles.Angles along the same non-parallel side add to 180°.
Question 3

Find angle in the trapezium.

Check answer
The top and bottom are parallel, so these two angles add to 180°.
Question 4

Find angle in the isosceles trapezium.

Check answer
The base angles are equal because the trapezium is isosceles.Angles along the same non-parallel side add to 180°.
Question 5

Find angle in the trapezium.

Check answer
The top and bottom are parallel, so these two angles add to 180°.
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