The angle and its elements
Two straight lines that are not contained in the same line, and have the same origin, divide the plane into two regions: one convex and one non-convex.
Each of these regions, together with the semi-straight ones, form a angle. Thus, the two straight lines determine two angles:
Every angle has two sides and a vertex. The sides are the straight lines that determine it. The vertex is the common origin of these semi-straights.
The convex angle of vertex O and sides is indicated by: AÔB, BÔA or Ô.
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