Perussektoorit
Perussektoorit are fundamental concepts in Finnish mathematics education, referring to the basic sectors of a circle. These are primarily the quarter circle and the semicircle. A quarter circle represents one-fourth of a full circle, subtending an angle of 90 degrees at the center. A semicircle represents one-half of a full circle, subtending an angle of 180 degrees at the center.
These basic sectors are introduced early in geometry lessons to build understanding of angles, areas, and circumferences
The terminology "perussektoorit" highlights their role as the most elementary divisions of a circle used in