Constructing Triangles Flashcards

All 5 cards in this deck

What are the steps to construct a triangle given its three sides (SSS)?
e.g. sides $7$ cm, $5$ cm and $4$ cm

1. Draw the longest side as the base: $7$ cm.
2. Set compasses to $5$ cm and draw an arc from one end; set to $4$ cm and draw an arc from the other end.
3. Join where the arcs cross to both ends of the base.

What are the steps to construct a triangle given two sides and the angle between them (SAS)?
e.g. sides $6$ cm and $5$ cm with an angle of $50°$ between them

1. Draw the $6$ cm side as the base.
2. Use a protractor at one end to measure $50°$ and draw a faint ray.
3. Mark $5$ cm along the ray and join that point to the other end of the base.

What are the steps to construct a triangle given two angles and the side between them (ASA)?
e.g. a side of $8$ cm with angles $40°$ and $65°$ at its ends

1. Draw the $8$ cm side as the base.
2. Measure $40°$ at one end and draw a line; measure $65°$ at the other end and draw a line.
3. Where the two lines cross is the third vertex.

You are given all three sides of a triangle. Which instrument fixes the position of the third vertex?

Compasses — draw arcs with radii equal to the two remaining sides from the ends of the base.

True or false? You should rub out the construction arcs once a triangle construction is finished, to make it neat.

False. All relevant arcs must be left showing, or full marks cannot be awarded.