Semicircle
A semicircle of radius r.
In geometry, a semicircle is a two-dimensional geometric shape that forms half of a circle. Being half of a circle's 360° (360 degrees), the arc of a semicircle always measures 180°. A triangle inscribed in a semicircle is always a right triangle.
Semicircle Media
Construction of a square with the same area as a given oblong
Comparison of Ford circles and a Farey diagram with semicircles for n from 1 to 9. Each semicircle intersects its corresponding circles at right angles. In the SVG image, hover over a circle or curve to highlight it and its terms.
An arbelos (grey region)
