92 HINTS TO TRAVELLERS. 
AC, and the difference of latitude B C is tlie co-sine to the same angle and 
radius. 
N 
S 
Problem III. —The distance between two places is generally resolved 
by plane trigonometry, the difference of latitude S L, and the azimuth, 
S'S L, called the course , forming a right-angled triangle, in which S S', the 
distance , is determined: the other side L S', termed departure , being the 
sum of all the meridional distances passed over. 
Problem IV. —Given the distance travelled on a given parallel of 
latitude to find the difference of longitude. 
Again, in the triangle A B C, let A B represent the distance or departure, 
c 
