SLA_DSEPV - Angle Between 2 Vectors

ACTION:

Angle between two vectors (double precision).

CALL:

D = sla_DSEPV (V1, V2)

GIVEN:

V1	D(3)	first vector
V2	D(3)	second vector

RETURNED:

sla_DSEPV

D

angle between V1 and V2 in radians

NOTES:

1. There is no requirement for either vector to be of unit length.
2. If either vector is null, zero is returned.
3. The result is always positive.