Section 3 - Interesting Shapes

Some other interesting things about shapes

a. Angles in triangles


b. Area of triangles


c. Pythagoras and triangles

...and finally let’s look at circles

a. Vocabulary of circles

b. Parts of a circle

c. Making circular patterns
You can make a pair of compasses from a strip of paper. This is called a ‘circle maker’. When you have made it, experiment with your own circular patterns

A closer look at polygons

a. Preparing yourself for drawing geometric constructions
Here are some of the basic rules necessary for geometric construction work. Some of them are very obvious, but train yourself to draw with good habits from the very beginning:

1. Wash your hands before starting any geometric work.
2. Make sure that your pencil is sharp.
3. Have a straight edged ruler with no rough edges.
4. If you have a pair of compasses, make sure that they are fairly stiff by tightening the central screw.
5. If you haven't a pair of compasses, make your own circle maker from paper orcard.
6. Practice making very light lines. Your pencil should just touch the paper lightly.
7. Using an eraser is very bad practice. It spoils the neatness of your work.
8. Keep all your constructions clean and accurate. Make sure you measure to the nearest millimetre.
9. Be proud of your work.
10. Enjoy making your constructions. It is a very satisfying skill.

b. Regular polygons
Regular polygons can be made from a number of triangles


c. Area of Polygons

d. Angles of quadrilaterals

e. Making patterns with polygons
Discover which polygons fit together like tiles without leaving any spaces. Find out why some polygons fit well while others do not.

Clue: It is something to do with the inner angle i.e. the inner angle of a hexagon is 120 degrees and hexagons fit well together. Why do some shapes fit together and others don’t?

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