330 APPENDIX CALCULATION OF THE 



THE OCTAHEDRON WITH a. RECTANGULAR BASE. 

 Fig. 343. 







Its elements. 



The inclination of the planes at the terminal edges 

 may be denoted by / t . 

 inclination of the plane P on P' 3 may be 



called / 2 . 

 ..... . . . M on M', . . . / 3 . 



Plane angle dfb, fig. 343, may be called A^ 

 and may be thus known, 



Plane angle b f e, being called A z , may be 

 thus determined, 



8 



K 



The first of these equations is thus derived. 

 The angle hfb in the above fig. represents 



M*. 



hfg ...... 90--I/.. 



bfi ....... -M*. 



gf* ...... 90-i/ 3 . 



But/g :fh :: R : sec. (90 | /,) 



fg: hb = gi::R: tang.(90'_l/ 3 ) 



