Constructing Triangles Flashcards

All 6 cards in this deck

Which instrument do you need to construct a triangle given three sides (SSS)?

Ruler and compasses (no protractor needed).

What are the steps to construct a triangle given three sides (SSS)?

e.g. sides 8 cm, 6 cm, 6 cm

1. Draw the longest side with a ruler: 8 cm
2. Set compasses to 6 cm, arc from one end
3. Set compasses to 6 cm, arc from the other end; join the crossing point to both ends

What are the steps to construct a triangle given two sides and the angle between them (SAS)?

e.g. sides 7 cm and 5 cm with a $40^\circ$ angle between them

1. Draw one side: 7 cm
2. Measure the angle at one end with a protractor: $40^\circ$
3. Measure the second side along that arm (5 cm) and join to complete the triangle

What are the steps to construct a triangle given two angles and the side between them (ASA)?

e.g. a 6 cm side with angles $50^\circ$ and $70^\circ$ at its ends

1. Draw the given side: 6 cm
2. Measure $50^\circ$ at one end and draw a long line
3. Measure $70^\circ$ at the other end and draw a line; they meet at the third vertex

True or false? When constructing a triangle you should rub out the compass arcs to make the drawing neat.

False. Construction arcs must be left visible or marks are lost.

What tolerance is normally allowed for accurate constructions and measurements?

Lengths within about $\pm 2$ mm and angles within about $\pm 2^\circ$.