! 18-ao.J GKOMKIiti' rnoSS 



space, on a surface, < me, are called 



the coordinates of the point. 



19. Analytic Geometry 1 mates may be represented 



munU-rs; tin- relation-^ ,!' th- \.i: 



and ill- various ge ligures which are 



ilioee points, can be through the corre- 



:isof liifsiealgehr.ti'- nut: ites, 



:.-NMM! ill thf form of al'J - 'platUM. 



. ill-- 111. till ..: 



f geonii 

 methods. 



a conveniently divided ii 



parts: Plane Analytic Geometry, which treats only of figures 



,;i\-n plane surface; and Solid Analytic Geometry, \vhii h 



'.'.rures, and includes / ieometry 



as a special ca** i plain- ai m^ th- 



simpler, will I.,- studied fir- I of this book, and 



II will )>< (Icvntcd t<> the Htudy of the solid anal 

 geon : tin- Mil.j.M t it will therefore 



be nnderstood that tlu* work is restricted to a given plane 



> of coordinates will be used, the Cartesian 



and the Polar ' >* are explained in the next few articles. 



20 Positive and negative coordinates. If a p>int lies in a 

 ;ht Inif, its position with reference to a 

 fixed point <f that line is com- 

 bined by one coor- x ' P' \ P JT 



dm, V l a VT, 



given ilneeted straight line, 



and let '> toward X be regarded as posit 



then distances from O toward X' are negative. A point /' 



