Curve
A curve is a line that turns or bends. A curved line is never straight, and a curved surface is a surface that is never flat. Some curves can be drawn on paper, but some curves, like a helix, can only be seen in 3-D. A circle is a curve that can be described with the formula x2 + y2 = r2. x and y are used as in a Cartesian coordinate system, and r is the radius of the circle (distance from the center to the outside). Many other curves can also be described with a formula like that.
Curve Media
A parabola, one of the simplest curves, after (straight) lines
Megalithic art from Newgrange showing an early interest in curves
The curves created by slicing a cone (conic sections) were among the curves studied in ancient Greek mathematics.
Analytic geometry allowed curves, such as the Folium of Descartes, to be defined using equations instead of geometrical construction.
A dragon curve with a positive area
