LAWS OF DECREMENT. 337 



OCTAHEDRON, RHOMBIC BASE. 



The ratio of an obtuse terminal edge 



: an acute terminal edge :: sin. A 3 : sin. A z . 

 Ratio of \ the axis : | the greater diagonal of 



base :: R : tang. A 6 

 \ the axis : * the lesser diagonal of 



base :: R : tang. A 5 

 -| the axis : the obtuse terminal edge 



:: cos. A 5 : R. 

 \ the axis : the acute terminal edge 



:: cos. A 6 : R. 

 obtuse terminal edge : perpendicular 



a /':: R : sin. A 2 . 



acute terminal edge : perpendicular 

 af:: R : sin.A 3 . 



Its units of comparison. 



The unit is rz 1, in reference to the following de- 

 crements. 



1. Simple and mixed on the terminal angles, pro- 

 ducing mod. b. 



2 obtuse lateral angles, 



producing mod. k. 



3 acute lateral angles, 



producing mod. q. 



4 . obtuse terminal edges. 



O 7 



producing mod. u. 

 5 acute terminal edges, 



producing mod. x. 

 6. edges of the base, 



producing mod. z. 



