Spherical Right Triangles

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Draw a spherical triangle on the surface of a unit sphere centered at
. Denote the arcs opposite the corresponding vertices as
,
,
. Let
,
,
be the angles at the vertices
,
,
. Suppose
, so that these become spherical right triangles. The following relations are then valid:
Contributed by: Izidor Hafner (March 2017)
Open content licensed under CC BY-NC-SA
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Details
Let be the orthogonal projection of
onto the edge
. Let
be the orthogonal projection of
onto
. Then
,
, but also
. Thus
.
,
, but also
. Thus
.
References
[1] Wikipedia. "Spherical Law of Cosines." (Mar 21, 2017) en.wikipedia.org/wiki/Spherical_law_of _cosines.
[2] Wikipedia. "Spherical Trigonometry." (Mar 21, 2017) en.wikipedia.org/wiki/Spherical_trigonometry.
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