344 APPENDIX CALCULATION OF THE 



RIGHT RHOMBIC PRISM. 



Let the ratio of the terminal to the lateral edge 



o 



be known and expressed by the ratio of m : n or of 



\: n -. 



m 



The general expression of the unit of comparison 

 will become 



s * T - in reference to simple or mixed decre- 

 n R 



ments on the terminal angle A of the pri- 

 mary form. This is evidently derived from 

 the ratio 



" A > 



, 



it 



ef:fl:: 1 : !L 

 m 



hence 



:: m cos. \A^ : n R. 



m sin. T^I^ j n reference to similar decrements on 

 n R 



the angle E of the primary form. 



For let 



R 



R m 



: n R. 



The ratios of the edges may be used as the units for 

 determining the laws of decrement producing the 

 planes belonging to the classes b and d of the modi- 

 fications of this form. 



