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
A semicircle with arithmetic and geometric means of a and b
An arbelos (grey region)
