2D shapes and circles
Parts of a circle and angles in polygons.
Circles all around
Wheels, plates and clocks are circles. Every point on a circle is the same distance from the centre. That distance is the radius.
Parts of a circle
Radius: centre to edge. Diameter: across through the centre = 2 × radius. Circumference: the distance all the way round.
Angles in polygons
Each triangle has angles adding to 180°. A pentagon splits into 3 triangles: 540°. Rule: (sides − 2) × 180°.
Regular polygons
A regular hexagon: 720° ÷ 6 = 120° at each corner. A regular pentagon: 540° ÷ 5 = 108°. Bees use hexagons because they fit together perfectly.
Properties, not looks
A square turned on its corner looks like a diamond, but it is still a square: 4 equal sides, 4 right angles. Classify shapes by their properties: equal sides, parallel sides, angles. Triangles with the same angles are similar; with the same sides and angles they are congruent.
What I learnt
- I can name parts of a circle.
- I can find angle sums of polygons.
- I can find angles in regular polygons.