144 GEOGRAPHIC TABLES AND FORMULAS. [bull. 234. 
Fornmla for using- quantities S and T: 
log sin a — log a" + ^S". 
log tan a — log a" + T. 
log cot a = a. c. log a" + a. c. log T. 
log «" = log sin a— S = log tan a— T. ■ 
log cos ^/. = log (90° - ^)" + S, 
log cot « ^ log (90° - «)" + T. 
log tan r^ = a. c. log (90° — a)" + a. c. log T. 
log (90° — a)" — log cos t^ — /S' = log cot a — T. 
