Classifying 2D shapes
Triangles and quadrilaterals by their properties.
Shapes in rickshaw art
Look closely at rickshaw art. You will find triangles of many kinds. We classify shapes by their sides and angles.
Types of triangle
Equilateral: 3 equal sides and 3 equal angles. Isosceles: 2 equal sides. Scalene: no equal sides. Right-angled: one angle is 90°.
Quadrilateral family
A square is a special rectangle AND a special rhombus. Rectangles and rhombuses are special parallelograms. A trapezium has exactly one pair of parallel sides.
Diagonals
A diagonal joins opposite corners. In a square, the diagonals are equal and perpendicular. In a rectangle, they are equal but not perpendicular.
Angles in a triangle
Tear the corners off a paper triangle and put them together: they make a straight line, 180°. If two angles are 60° and 70°, the third is 180 − 130 = 50°. Triangles: equilateral, isosceles, scalene.
Circles
Every point on a circle is the same distance from the centre: the radius. The diameter goes across through the centre: 2 × radius. Congruent shapes are identical; similar shapes are the same shape in a different size.
What I learnt
- I can classify triangles.
- I can classify quadrilaterals.
- I can use diagonals and perpendicular lines.