408 Prof. G. M. Minchin's Graphic Representation 



which equation denotes an hyperbola, AjpQP, making an inter- 

 cept, OA, on the axis of y such that 



2 



OA=^ 



(4) 



Call this curve the 'primary hyperbola. 

 7 



V 



then 



In the same way, let I /2 be denoted by tf 



k 2 Wxy r = (r ± r 2 - A 2 ^) 2 + B%, .... (5) 



showing that the values of I /2 are also represented by the 

 ordinates of an hyperbola, BHF. We shall discuss this 

 hyperbola more particularly, and show that it may be easily 

 and rapidly drawn. Call it the secondary hyperbola. In the 



B 4 



first place, it passes through the point x: 



r x r 2 ,_ xr , 



A> y ~k 2 W ; 



the tangent at this point is parallel to Ox. The point is H, 



