Angle unit

A spherical triangle is determined by four quantities, usually by the radius of the sphere `R`
and three further quantities. If the radius of the sphere is not specified,
the computation will be successful only in rare cases. All angles `α,β,γ` of the triangle must be less than *π = 180° = 200 gon*
.
The triangle is not always uniquely determined. In non-unique cases both solutions will be displayed.

If the quantities `a,b,c,s,r _{u},r_{i}`
are terrestrial arc lengths in m or km, we recommend the radius

If these quantities are specified or desired as angles in degrees, the radius should be