Lines, angles and triangles

Learning objectives

Use angle relationships at a point, on a straight line, in vertical pairs and between parallel lines cut by a transversal

Apply the angle sum of a triangle, the exterior angle theorem and the interior angle sums of polygons

Use the properties of isosceles and equilateral triangles and the link between side lengths and the sizes of opposite angles

Decide whether two triangles are congruent or similar and use corresponding parts and scale factors to find missing lengths and angles

Apply the triangle inequality and reason about the possible side lengths of a triangle