Classifying Triangles

Every triangle gets two names, one from its sides (equilateral, isosceles or scalene) and one from its angles (acute-angled, right-angled or obtuse-angled). In NSW Year 8 maths (NESA outcome MA4‑GEO‑C‑01) the sides or angles usually have to be worked out before the triangle can be named.

You will change sides to one unit before comparing them, find all three angles from the angle sum or an exterior angle, and use the fact that equal sides sit opposite equal angles. You will classify triangles on the number plane using Pythagoras' theorem, solve for sides and angles given as expressions, count axes and the order of rotational symmetry, and classify the end of a roof truss. It is part of Year 8 Geometry.