Concept 8 of 10Foundation
Watch on YouTubeVideoConstructing triangles (SSS, SAS, ASA, RHS)
Four kinds of information uniquely determine a triangle:
- SSS (Side-Side-Side): all three sides known
- SAS (Side-Angle-Side): two sides + the angle BETWEEN them
- ASA (Angle-Side-Angle): two angles + the side BETWEEN them
- RHS (Right-angle-Hypotenuse-Side): special for right triangles
SSS example — triangle with sides 4, 5, 6 cm:
- Draw base AB = 6 cm (the longest, for stability).
- With compass at A and radius 4, draw an arc above AB.
- With compass at B and radius 5, draw an arc cutting the first.
- Label intersection C; join AC and BC. Done!
SAS example — ∠B = 60°, AB = 5, BC = 7:
- Draw AB = 5.
- At B, construct a 60° angle.
- Mark C along that ray at 7 cm from B.
- Join AC.
Example
Why does SSS work? Three sides determine a rigid shape (that's why triangles are used in bridges — they don't wobble). Give me three exact side lengths, and only ONE triangle exists (up to flipping).
💡 Tip:Triangle inequality (a + b > c) MUST be checked before you try SSS. If it fails, the arcs won't meet.
▶Prefer a video? Open YouTube search for “triangle construction SSS SAS ASA class 6”↗🎯 Try it!
5 questions to check what you just read.
0 / 5
- Q1.Minimum pieces of info to construct a unique triangle:
- Q2.SAS means:
- Q3.Can a triangle have sides 3, 4, 8?
- Q4.Triangle with sides 3, 4, 5 is:
- Q5.To construct triangle with given 3 sides, the case is: