Let the points of intersection of the line and the ellipse be (acosθ,bsinθ) and {acos(
π
2
+θ),bsin(
π
2
+θ)}, since they lie on the given line bx+my+n=0 lacosθ+mbsinθ+n=0 ⇒ lacosθ+mbsinθ=−n and lasinθ+mbcosθ+n=0 lasinθ−mbcosθ=n squarring and adding, we get, a2l2+b2m2=2n2 ⇒