function x = DY(y)

     x(1) = y(2)*y(3)/sum(y) ;
     x(2) = y(1)*y(3)/sum(y) ;
     x(3) = y(1)*y(2)/sum(y) ;
     
     %this does the Delta-Y transformation, where the input is a vector of
     %the resistances of the Delta graph in counter clockwise order, and
     %the output is the vector of the resistances of the inverted Y graph.

