Plane angle and Solid Angle

  
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is the solid angle at the centre of a sphere subtended by a portion whose surface area is equal to the square of its radius of the sphere.

is the angle between the intersection of two straight lines or intersection of two planes.

The SI unit of Plane Angle is ‘’ and is denoted as ‘’.

π radian =

The SI unit of solid angle is ‘’ and is denoted as ‘’.

is the angle subtended at the centre of a circle by an arc whose length is equal to the radius of the circle.