# Constants - Orbifold/XAct GitHub Wiki

The Constants class contains all sorts of mathematical, numerical and useful constants.

• Catalan: the Catalan number
• Euler: the Euler constant
• EulerGamma: the Euler-Mascheroni constant
• Glaisher: the Glaisher-Kinkelin constant
• GoldenRatio: the golden ratio
• InverseEuler: the inverse of the Euler constant (i.e. 1/e)
• InversePi: the inverse of Pi (i.e. 1/pi)
• InvSqrt2Pi: the inverse of square root of twice pi ( i.e. 1/Sqrt(2*Pi))
• InvSqrtPi: the inverse of the square root of Pi(i.e. 1/Sqrt(Pi))
• Khinchin: the Khinchin constant
• Log2E: the log of the Euler constant in base 2 (i.e. log(2)(e))
• Ln2: the log of two in the natural base (i.e. log(e)(2))
• Ln10: the log of ten in the natural base (i.e. log(e)(10))
• LnPi: the log of pi in the natural base (i.e. log(e)(10))
• Pi: the pi constant (150 digits precision)
• Sqrt1Over2: the square root of 0.5
• Sqrt2: the square root of two
• Sqrt2Pi: the square root of twice pi
• Sqrt3DividedBy2: the square root of three divided by two
• PiOver180: pi divided by 180 (the degree to radians conversion factor)
• PiOver2: pi divided by 2
• SqrtPi: the square root of pi
• PiOver4: pi divided by 4
• SpeedOfLight: the speed of light in vacuum
• PlancksConstant: the Planck constant
• PlancksLength: the Planck length
• GravitationalConstant: the gravitational constant
• MagneticPermeability: the magnetic permeability in vacuum
• ElectricPermitivity: the electric permitivity in vacuum