Geometry for elementary school/Notation

This chapter summaries the notation used in the book. An effort was made to use common conventions in the notation. However, since many conventions exist the reader might see a different notation used in other books.

One who is interested seeing an example of past notation might be interested in Byrne's edition of Euclid's Elements. See for example the equilateral triangle construction.

Point

A point will be named by a bolded English letter, as in the point A.

Line segment

We will use the notation $\overline{AB}$ for the line segment the starts at A and ends at B. Note that we don't care of the segment direction and therefore $\overline{AB}$ is similar to $\overline{BA}$.

Angle

We will use the notation $\mathrm{\angle }ABC$ for the angle going from the point B, the intersection point of the segments $\overline{BA}$ and $\overline{BC}$.

Triangle

A triangle whose vertices are A, B and C will be noted as $\mathrm{△}ABC$. Note that for the purpose of triangles' congruence, the order of vertices is important and $\mathrm{△}ABC$ and $\mathrm{△}BCA$ are not necessarily congruent.

Circle

We use the notation $\circ A,\overline{BC}$ for the circle whose center is the point A and its radius length equals that of the segment $\overline{BC}$.

Note that in other sources, such as Euclid's Elements, a circle is describe by any 3 points on its circumference, ABC.

The center, radius notation was chosen since it seems to be more suitable for constructions. it:Geometria per scuola elementare/Notazione