ASTRONOMY. 



Find an angle x, so that 



tan x = cos z X cot a, then 



7 tan z X sin x 



tan // = ; 



cos ( x) 



COS X 



In applying these formulas it must be observed, that 

 when z, or the azimuth counted from the north, is 

 greater than 90, cos z 9 and therefore also tan x 9 

 and x itself, are negative. 



The latter formula is useful, when the declination of 

 a star is to be determined, and the former when 

 the time is to be determined from the observations 

 of a star not in the meridian. It is more usual, 

 however, when the time is required, to have the 

 declination of the star given, as in the following 

 problem. 



23. The declination and the altitude of a star 

 being given, as also the latitude, to find the 

 horary angle and the azimuth. 



Here the three sides of the triangle ZPS are given, 

 to find the angles at P and Z. 



If d f = complement of Dec. 

 a' = complement of Alt. 

 I' = complement of Lat. 



sin 



