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Ellery W. Davis 



From the formula and the construction for the distance between 

 two points we can derive that for the distance from a line to a 

 point. We have only to pass through the point a line perpendicular 

 to the given line, find where this intersects the given line and 

 then get the distance between the given point and this point of 

 intersection. If the line, referred to rectangular axes be 



ax + by -\-c = o, 



while the point is (x 1 y\) this will be found to give for the dis- 

 tance desired 



Va 2 -\-l 2 



Suppose that referred to rectangular axes through O, the center 

 of the line, the equation becomes 



y = c i 4,x. 

 Then with (i, c i( t>) determines the line. Similarly with 



(1, *»♦) /S 



Fig. 2i. 



( — <? 2 *, i) determines a line related to axes OY and the opposite 

 of OX precisely as the above line is to OX, and OY; the line, 



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