Definition:Inner Angle of Spherical Triangle
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Definition
Let $\triangle ABC$ be a spherical triangle on the surface of a sphere whose center is $O$.
Let the sides $a, b, c$ of $\triangle ABC$ be measured by the angles subtended at $O$, where $a, b, c$ are opposite $A, B, C$ respectively.
Consider the $4$ consecutive parts of $\triangle ABC$:
- $B, a, C, b$
Then $C$ is known as the inner angle of $B, a, C, b$
Also see
Sources
- 1976: W.M. Smart: Textbook on Spherical Astronomy (6th ed.) ... (previous) ... (next): Chapter $\text I$. Spherical Trigonometry: $8$. The four-parts formula.