Geometry and measuresKey Stage 3

Angles in an equilateral triangle

Use the fact that every interior angle is 60°.

  • All three sides and all three angles are equal.
  • Each interior angle is .
  • If a corner is split, its smaller angles still add to .

Example 1

Find angle in the equilateral triangle.

All three angles are equal.

Example 2

Find angle in the equilateral triangle.

The exterior angle and the 60° interior angle lie on a straight line.

Your turn

Question 1

Find angle in the equilateral triangle.

Check answer
The whole corner of an equilateral triangle is 60°.
Question 2

Find angle in the equilateral triangle.

Check answer
The whole corner of an equilateral triangle is 60°.
Question 3

Find angle in the equilateral triangle.

Check answer
The whole corner of an equilateral triangle is 60°.
Question 4

Find angle in the equilateral triangle.

Check answer
The whole corner of an equilateral triangle is 60°.
Question 5

Find angle in the equilateral triangle.

Check answer
The whole corner of an equilateral triangle is 60°.
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