Loci and constructions

3) Constructing triangles

Triangles and other shapes can be accurately constructed using a protractor, a pair of compasses and a ruler.

In order to draw a triangle, three properties are needed:

SAS – Side Angle Side
ASA – Angle Side Angle
SSS – Side Side Side


Constructing triangles given SAS

The lengths of two sides and the size of the angle in between are needed.

Make an accurate drawing of a triangle with lengths 4 cm and 6 cm with an angle of 40° in between.


Constructing triangles given ASA

The sizes of two angles and the length of the side in between are needed.

Make an accurate drawing of a triangle with the angles 40° and 70°, with a side of length 8 cm in between.


Constructing triangles given SSS

The lengths of all three sides are needed.

Make an accurate drawing of a triangle with sides of length 3 cm, 5 cm and 6 cm.

As with all constructions, ensure that the construction lines are not rubbed out. These show that the triangles were accurately constructed.


Exercise | Answer Keys
Loci and Transformationsexam-styled questions (PDF)

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