apothem

n. bisector crossing from one side of a polygon to another side (Geometry)

The apothem of a regular polygon is a line segment from the center to the midpoint of one of its sides. Equivalently, it is the line drawn from the center of the polygon that is perpendicular to one of its sides. The word "apothem" can also refer to the length of that line segment. Regular polygons are the only polygons that have apothems. Because of this, all the apothems in a polygon will be congruent and have the same length.
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(n.)
The perpendicular from the center to one of the sides of a regular polygon.
  

(n.)
A deposit formed in a liquid extract of a vegetable substance by exposure to the air.
  

apothem /'æpəθem/
danh từ (toán học) đường trung đoạnapothem of a regular polygon: trung đoạn một hình nhiều góc đều
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APOTEMA