**ACTION:**- Angle between two points on a sphere (single precision).
**CALL:**`R = sla_SEP (A1, B1, A2, B2)`

**GIVEN:**-

*A1,B1***R**spherical coordinates of one point (radians) *A2,B2***R**spherical coordinates of the other point (radians)

**RETURNED:**-

*sla_SEP***R**angle between [A1,B1] and [A2,B2] in radians

**NOTES:**- 1.
- The spherical coordinates are right ascension and declination,
longitude and latitude,
*etc.*in radians. - 2.
- The result is always positive.

Starlink User Note 67

P. T. Wallace

12 October 1999

E-mail:ptw@star.rl.ac.uk