Lesson 7 of 9

The big picture

3 min

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Here is the whole track on one page.

Playing with Constructions — the whole chapter on one screen
Idea	Remember	Example
Exact, not neat	A construction passes its check. A drawing by eye may not.	Sides 40, 40, 40, 42 mm: one is off.
The circle	Every point is one radius from the centre.	An oval fails. A compass ring passes.
Across the middle	The diameter is the radius twice over.	Radius 30 mm gives diameter 60 mm.
Carrying a length	The compass span holds a length. No number is read.	An arc from C copies AB.
Square corners	Equal marks on both arms. Measure the gap.	30 mm marks leave a gap of 42 mm.
Steps in order	A step needs what it uses to be there first.	A shut compass cannot swing an arc.

Open your book to Chapter 8, Playing with Constructions. You have already done each of these.

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