viisnurk

Viisnurk is the Estonian word for a pentagon, a five-sided polygon. Like any polygon, a pentagon is a two-dimensional closed shape made up of straight line segments. A regular pentagon has five equal sides and five equal interior angles. The sum of the interior angles of any pentagon, regardless of whether it is regular or irregular, is 540 degrees. In a regular pentagon, each interior angle measures 108 degrees. The exterior angles of a regular pentagon each measure 72 degrees, and their sum is also 360 degrees.

Pentagons can be convex or concave. A convex pentagon has all its interior angles less than 180 degrees, meaning all its vertices point outwards. A concave pentagon has at least one interior angle greater than 180 degrees, causing at least one vertex to point inwards. The study of geometric shapes like the viisnurk is fundamental to geometry and has applications in various fields, including architecture, art, and design, where pentagonal shapes are often found. The construction of a regular pentagon can be achieved using a compass and straightedge, a classic geometric construction problem.