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.