APPENDIX CALCULATION OF THE 



RHOMBOID. 



The superior plane angles may be called^,, and 

 may be thus found, 



The angle f A l is one of the sides of the 

 spherical triangle marked on fig. 357, whose 

 angles are evidently 90, 60, and | /,. The 

 general formula to determine \ A l is 



cos. i A. = "I^OL 

 sin. * /, 



O 



but as cos. 60 ~ , the formula becomes 



2 sin. |/ t 



Lateral plane angles will be (180 n A,) and 

 may be called A a . 



Inclination of the superior edge to the axis 

 may be called A^ and may be thus found, 



The angle b dn, fig. 357, is the inclination 

 required, and is the hypothenuse of the tri- 

 angle already used, whence 



nn. * - C0t - CQ1 C0t - J J . 

 R 



Inclination of the oblique diagonal to the axis 



may be denoted by A 4 , and may be thus fo md, 



The angle e d n which we call A 4 , is the 



third side of the triangle marked on the 



figure, and may consequently be determined 



from the formula, 



cos. A . ' CQS> T- - 



sin. 60 



Sum of the two preceding angles, being the 

 inclination of an oblique diagonal to a superior 

 edge, when measured over the summit, may 

 be denoted bv A f . 



