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So for 2D angles (radians), the measure of the angle is equal to length of the subtended arc of the unit circle.

Can we define 3D angles to be the area subtended by the angle on the unit sphere?

For example, the 3D angle measure of one corner of a cube is $1/8 \times 4\pi = 1/2\pi$

user137794
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1 Answers1

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solid angle/steradian are the terms used for this concept you can read more about them here http://en.wikipedia.org/wiki/Solid_angle

ruler501
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