PROBLEMS. 



42S. 



centre C, will give the divisions of the line of secants > 

 which must be numbered from A toward F with lo, 20j 



-3 0, &C. 



7« To construct the Lifte of Semitangenfs^ or the Tattgents of 

 half the Arcs, 



A riile on E, and the several divisions of the arc A D, 

 -vlil intersect the' rndius C A, in the divisions of the semi 

 •or half tangent<5 j mark these with the corresponding fig- 

 ures of the arc A D. 



U iiC fcermtangents on the plane scales are generally con- 

 tinued as far as the length of the rule, on which they arc 

 Inid, will adrjir ; the divisions beyond 90° are found by 

 dividing tive arc A E like the arc AD, then laying a rule 

 by E and these divisions of the arc AE, the divisions of 

 the semitiingents above '90 degrees v.'lli be obtained on the 

 fine C A continued. 



8. To construct the Line (f LorgituJr, 



Dlvitk AH into 60 equal parts ; through each of these 

 divisions parallels to the radius AC, will intersect the 

 arc AE in as many points ; from E, as a centre, the di- 

 visions jjf the arc EA, being transferred to the chord EA, 

 w-iil give the divisions of the line of longitude. 



The points thus found on tlie quadrantal arc, taken 

 'from A to E, belong to the. sines of the equally increas- 

 ing sexagenary parts of the radius j and fho:3e s.rcs, reck- 

 oned 

 Fpf 



