GKOMKi r I ION* ::i 



nated by P, and iU coordinate* ). ) or (/>, 0). If 



M-\iT.il \.in.iM-- |...mts an- untiei OOnrfdtnlkNI .1. ti:- NflM 

 , th.-v >11 be designated l.x /'/'./'./' 

 nates by (* y), 



Fixed poinu 



will be designated l /',, , ami tl-ir roonlinau 



.Vi), ^ r or by 0> P ^ 



II. ELBMKNTARY API'I.K Al ION8 



25. I iu- UK -thods of representing a point in a plane that 

 have been adopted in the previous articles lead at once to 

 several easy ap]>li< .iti<tis, such as finding the distance be- 

 tween two points, the area of a triangle, etc. The form of 

 the results will depend upon the particular system of coordi- 

 nates chosen, 1'ut the method is the same in each case. 



. as in tli.- more difficult problems that arise later, to 



full advantage of tin- an.ih ti.- iu'-th<><l lent 



M freely use geometric con- m to guide his alge- 



lut he should, at the same time, see clearly that 



the method is essentially algebra 



26. Distance between two points. 



(1) Polar codniinatet initial lint-,* the 



l\ = (p r 0j) and /*,= (p r 0,) be the two p: 



* Till' 'I' 111 '!.-! T.lt !< >!l ;l{<' l !li' t 



