puoliympyrän

Puoliympyrä is the Finnish word for semicircle. A semicircle is a one-dimensional locus of points that forms half of a circle. It is defined by a diameter and the arc connecting the endpoints of that diameter. The diameter is the straight line segment that passes through the center of the circle and has its endpoints on the circle's circumference. The arc is the curved portion of the circumference.

The circumference of a full circle is given by the formula C = 2πr, where r is the radius. The arc length of a semicircle is therefore half of this, or πr. The perimeter of a semicircle includes both the arc length and the diameter. Thus, the perimeter of a semicircle is πr + 2r, which can be factored as r(π + 2).

In geometry, semicircles are fundamental shapes used in various constructions and calculations. They appear in designs, architecture, and in the study of areas and volumes. For example, the area of a semicircle is half the area of a full circle, which is (1/2)πr². The concept of a semicircle is a straightforward application of circular geometry.