116
Polygons
Textbook Part 4, pp. 12–13
GoalTell closed from open broken lines; name polygons by their number of corners.
New words
polygon · ko‘pburchakvertex (corner) · uchside · tomonclosed / open · yopiq / ochiqpentagon · beshburchak
Explanation
A shape enclosed all round by a closed broken line is a polygon. Its name comes from its number of corners: 3 — triangle, 4 — quadrilateral, 5 — pentagon, 6 — hexagon. A polygon has as many sides as corners.
Worked examples
An animal pen is like a closed broken line — it is a polygon. If one fence is broken, the line becomes open.
Honeycomb cells are hexagons (6 corners, 6 sides).
Class activity
Build with sticks: children make closed shapes from 3, 4 and 5 sticks and name them. What if one stick is removed? (An open broken line.)
Practice
1
What is a polygon with 5 corners called?
Pentagon
2
How many sides does a hexagon have?
6
3
Is a circle a polygon?
No — its edge is a curve
4
Broken line: the first link is 45 cm and the second 12 cm shorter. Total length?
78 cm