| dφ | = | dw | , Q | ds | = | dφ | = | dw | | du | , |
| du | du | dθ | dθ | du | dθ |
| πQ | | ds | = | π | | ds | = | (cos α − cos β) (cos α − cos β′) sin θ | , |
| m + m′ | dθ | c | dθ | (cos α − cos θ) (cos θ − cos β) (cos θ − cos α′) |
| = | sin θ | + | cos α − cos β′ | · | sin θ |
| cos α − cos θ | cos β − cos β′ | cos θ − cos β |
| cos α − cos β | · | sin θ | , |
| cos β − cos β′ | cos θ − cos β′ |
(7)
giving the intrinsic, equation of the surface of a jet, with proper attention to the sign.
From A to B, a > u > b, θ = 0,
| ch Ω = ch log | Q | = cos α − ½ sin2 α | a − a′ |
| q | a − b |
| sh Ω = sh log | Q | = | √ (a − u·u − a′) | sinα |
| q | u − b |
| Q | = | (u − b) cos α − ½ (a − a′) sin2 α + √ (a − u·u − a′) sin α |
| q | u − b |