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 Physics Areas of Physics Interdisciplanary areas of physics Quantities in Physics Base Units Convention for indicating units Derived Units S.I. Units (International System of Units) Supplementary units Homogeneity of equations Significant figures Rules of Significant figures Further discussion on Significant figures Dimensions Scientific notation The Avogadro's Constant Scalars and Vectors Addition and subtraction of co-planar vectors Rectangular components of a vector

## Supplementary units

The General Conference on Weights and Measures has no yet classified certain units of the SI under either base units or derived units., These SI units are called supplementary units. For the time being this class contains only two units of purely geometrical quantities, which are plane angle and the solid angle.

The radian is the plane angle between two radii of a circle which cut off on the circumference an arc, equal in length to the radius.

(one radian is just under 57.3 degrees)

The Steradian is the solid angle (three dimensional angle) subtended at the centre of a sphere by an area of its surface equal to the square of radius of the sphere.

(There are 4 pi, or approximately 12.5664,steradians in a complete sphere)

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