Definition:Spherical Triangle/Side

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The sides of a spherical triangle $T$ are the arcs of the $3$ great circles which form the boundaries of $T$ between the points at which they intersect.


In the above diagram, the sides are labelled $a$, $b$ and $c$.

Length of Side

Let $ABC$ be a spherical triangle on a sphere $S$.

Let $AB$ be a side of $ABC$.

The length of $AB$ is defined as the angle subtended at the center of $S$ by $AB$.