Constructing triangles | Maths | Quizalize & Oak National Academy

Starter quiz

Match the angle size to the type of angle.
- $12^\circ$
  
  ⇔
  
  acute angle ✓
- $90^\circ$
  
  ⇔
  
  right angle ✓
- $138^\circ$
  
  ⇔
  
  obtuse angle ✓
- $305^\circ$
  
  ⇔
  
  reflex angle ✓
Which of these sketched triangles are definitely isosceles?
Lucas has used a centimetre ruler to draw a line of 8.2 cm. Which image shows his line?
Which of these shows the best set up of a pair of compasses?
An arc of a circle is part of the circle’s ______.
- 'circumference' ✓
A triangle has a perimeter of 65 mm. Two of the edges are 23 mm and 26 mm respectively. How long is the third edge of the triangle?
- 15 mm
- 16 mm ✓
- 17 mm
- 18 mm
- 19 mm

Which description matches this sketch?
- Triangle PQR, where PQ = 7 cm, PR = 12 cm and QR = 14 cm
- Triangle PQR, where PQ = 7 cm, PR = 14 cm and QR = 12 cm
- Triangle PQR, where PQ = 12 cm, PR = 14 cm and QR = 7 cm ✓
- Triangle PQR, where PQ = 14 cm, PR = 7 cm and QR = 12 cm
- Triangle PQR, where PQ = 14 cm, PR = 12 cm and QR = 7 cm
When constructing a triangle from three edge lengths, we use a pair of compasses to draw ______ circles.
- 'intersecting' ✓
Which of the following shows a partial construction of an equilateral triangle?
Which of the following lengths could be the edge lengths of a triangle?
- 3 cm, 4 cm and 5 cm ✓
- 3 cm, 3 cm and 6 cm
- 8 cm, 8 cm and 8 cm ✓
- 7 cm, 9 cm and 18 cm
- 9 cm, 9 cm and 14 cm ✓
Which of the points C, D or E when connected to AB would create a triangle with three edges of different lengths?
- C ✓
- D
- E
Triangle ABE is an ______ triangle.
- 'isosceles' ✓

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A construction is an accurate drawing made using geometrical properties.
A scalene triangle can be constructed using intersecting circles with different radii.
An equilateral triangle can be constructed using intersecting circles with equal radii.
An isosceles triangle can be constructed using intersecting circles.

Pupils may avoid using the pair of compasses and opt for a ruler instead.

Emphasise the efficiency and accuracy of using compasses instead of a ruler in the construction of their triangles.

Scalene triangle - Scalene triangles have three different-sized angles and three edges of different lengths.
Isosceles triangle - Isosceles triangles have two equal-sized angles. Two of the edges are equal in length.
Equilateral triangle - Equilateral triangles have three equal-sized angles and three edges of equal length. They are regular triangles.
Radius - The radius is any line segment that joins the centre of a circle to any point on its circumference.