The golden angle is the angle subtended by the smaller (red) arc when two arcs that make up a circle are in the golden ratio
In geometry, the golden angle is the smaller of the two angles created by sectioning the circumference of a circle according to the golden section; that is, into two arcs such that the ratio of the length of the larger arc to the length of the smaller arc is the same as the ratio of the full circumference to the length of the larger arc.
Algebraically, let a+b be the circumference of a circle, divided into a longer arc of length a and a smaller arc of length b such that
The golden angle is then the angle subtended by the smaller arc of length b. It measures approximately 137.5077640500378546463487 ...° A096627 or in radians 2.39996322972865332 ... A131988.
The name comes from the golden angle's connection to the golden ratioφ; the exact value of the golden angle is
where the equivalences follow from well-known algebraic properties of the golden ratio.