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The angle A (respectively, B and C) may be regarded either as the dihedral angle between the two planes that intersect the sphere at the vertex A, or, equivalently, as the angle between the tangents of the great circle arcs where they meet at the vertex. Angles are expressed in radians.
The distances between the centers of the nearer and farther circles, O 2 and O 1 and the point where the two outer tangents of the two circles intersect (homothetic center), S respectively can be found out using similarity as follows: Here, r can be r 1 or r 2 depending upon the need to find distances from the centers of the nearer or farther ...
The surface area of a spherical lune is 2θ R 2, where R is the radius of the sphere and θ is the dihedral angle in radians between the two half great circles. When this angle equals 2π radians (360°) — i.e., when the second half great circle has moved a full circle, and the lune in between covers the sphere as a spherical monogon — the ...
In the extrinsic 3-dimensional picture, a great circle is the intersection of the sphere with any plane through the center. In the intrinsic approach, a great circle is a geodesic; a shortest path between any two of its points provided they are close enough. Or, in the (also intrinsic) axiomatic approach analogous to Euclid's axioms of plane ...
Angle AOB is a central angle. A central angle is an angle whose apex (vertex) is the center O of a circle and whose legs (sides) are radii intersecting the circle in two distinct points A and B. Central angles are subtended by an arc between those two points, and the arc length is the central angle of a circle of radius one (measured in radians). [1]
The polar angle may be called inclination angle, zenith angle, normal angle, or the colatitude. The user may choose to replace the inclination angle by its complement , the elevation angle (or altitude angle ), measured upward between the reference plane and the radial line—i.e., from the reference plane upward (towards to the positive z-axis ...
Let u, v, and w denote the unit vectors from the center of the sphere to those corners of the triangle. We have u · u = 1, v · w = cos c, u · v = cos a, and u · w = cos b.The vectors u × v and u × w have lengths sin a and sin b respectively and the angle between them is C, so = () = () () =
The previous case can be extended to cover the case where the measure of the inscribed angle is the difference between two inscribed angles as discussed in the first part of this proof. Given a circle whose center is point O, choose three points V, C, D on the circle. Draw lines VC and VD: angle ∠DVC is an inscribed angle.