Geometry for Elementary School/Our tools: Ruler and compass
How to draw a line
We will use the notation for the line segment the starts at A and ends at B. Note that we don't care about the segment direction and therefore is the same as .
How to draw a circle
- Using the compass (based on Book I, Postulate 3).
We use the notation for the circle whose centre is the point A and its radius length equals that of the segment .
Note that in other sources, such as Euclid's Elements, a circle is described by any 3 points on its circumference, ABC.
The center-radius notation was chosen because of its suitability for constructing circles with a ruler and a compass.