radian
Suppose that a circle of radius 1 with centre O meets two half-lines from O to A and B. Then the size of ∠AOB, measured in radians, equals the length of the arc AB.
On a unit circle, the arc AB equals ∠AOB in radians
1 radian is approximately 57°. More accurately, 1 radian≈57.296°≈57° 17′45″. Since the circumference of a unit circle is 2π, one revolution or 360° measures 2π radians. Consequently, x° = πx/180 radians.
The radian is the SI unit for measuring angle.
Compare steradian.
- diagonal matrix
- diagram
- diameter
- diameter
- diameter of a set
- diamond
- dichotomy
- dichotomy paradox
- die
- diffeomorphism
- difference
- difference equation
- difference of two sets
- difference of two squares
- difference quotient
- difference sequence
- differentiable function
- differentiable function
- differential calculus
- differential equation
- differential form
- differential geometry
- differential operator
- differential topology
- differentiation