{$DS.}Function FFORMA3D13(L,H,D) X=D/L Y=H/L A=1/sqrt(1+(Y/X)^2) B=1/sqrt(X^2+Y^2) FFORMA3D13=(1/(2*pi))*((arctan(1/X)*Convert(deg,rad))-(A*arctan(B)*Convert(deg,rad))) End