I + I I 



- |h I - ^<L< - |hJ - — ^ 



o m Ih I m h 



o o' o o 



with the left-hand inequality coming from the first of the basic inequalities 

 and the right-hand inequality from the second. (Note that h /|h | = |h |.) 



Thus, h and L may both be positive, as drawn in Figure h ; if h < 0, 

 L must be negative also. 



