question: public static double distancePointLinePerpendicular ( Coordinate p , Coordinate A , Coordinate B ) { double len2 = ( B . x - A . x ) * ( B . x - A . x ) + ( B . y - A . y ) * ( B . y - A . y ) ; double s = ( ( A . y - p . y ) * ( B . x - A . x ) - ( A . x - p . x ) * ( B . y - A . y ) ) / len2 ; return Math . abs ( s ) * Math . sqrt ( len2 ) ; }
target:  Computes the perpendicular distance from a point p to the (infinite) line containing the points AB