1888 - 89 .] Dr E. Sang on Fundamental Tables. 
255 
The convenience of having the true anomaly, and the planet’s 
distance alongside of the time-argument, would be so great as to 
dwarf altogether that of having merely the angle of position ; this 
last mentioned forms, indeed, only a step toward the obtaining of 
the others. The remaining operation, implying only the solution 
of a right-angled triangle, is easy though laborious. It may, there- 
fore, be not inopportune to indicate here the course most convenient 
to be followed in the subsequent work; particularly because that 
which may appear to be the most rapid in an isolated case, may not 
be the best for systematic work. 
Distances. 
If P be the planet’s place in the ellipse AsA's', having S and S' 
for its foci, and SS' for its minor axis, and if the ordinate HP be 
a 7 
continued to meet the circle described on AA' as a diameter in Q, 
the arc AQ is p, the arc of position, and we have 
SIT = cosj9 - cos e ; PH = sin^>. sin e. 
