If the locus of the mid points of the chords of the ellipse $\frac{{\mathrm{x}}^2}{{\mathrm{a}}^2}+\frac{{\mathrm{y}}^2}{{\mathrm{b}}^2}=1,$  drawn parallel to $\mathrm{y}={\mathrm{m}}_1\mathrm{x} \mathrm{is} \mathrm{y}={\mathrm{m}}_2\mathrm{x} \mathrm{then} {\mathrm{m}}_1{\mathrm{m}}_2 =$