Steps that have to wait
To build a rectangle, some steps can go first. Some must wait.
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The rule
A step can only start when what it needs is already there.
To rule a line is to draw it with a ruler. An upright is a line that stands straight up from the base.
Step 1 of 7
- Rule the base, A to B.
- Open the compass to the height.
- Raise a square-corner upright at A.
- Raise one at B too.
- Mark the height up A's upright.
- Mark the height up B's upright.
- Join the two marks to close it.
Example
Ruling the base and opening the compass need nothing else. Either can go first.
Marking the height needs an upright and an open compass. It must wait for both.
In the lab, drag the five step cards into order. Then run them. A step that must wait stops the run.