👉 The term "arctoid" is a mathematical concept that refers to the angle in radians between two lines. Specifically, it describes the angle formed by the line connecting two points on an infinite number of circles, such as the unit circle (the set of all points with a given radius and arc length) or the complex plane (a 2-dimensional surface). The arctangent function, also known as tan-1, is defined for any real number x to return the angle θ in