APPENDIX TO CHAPTER XII 361

“slope” of the secant AB in relation to the ordinate ad
(32+ ad), Similarly, the slope of the secant AC drawn
through points corresponding to times a half year apart, taken

in relation to a4, is the rate of interest reckoned semi-annually,

 

g'

 

 

 

Fic. 33.

and so on. At the limit, the slope of the tangent AT (in relation
 to aA) represents the rate of interest reckoned continuously.

Similarly, the regressive secant, 4B', represents the rate of
discount, reckoned annually (if ab' represents a year interval),