What is "supplementary chords"

Supplemental \Sup`ple*men"tal\, Supplementary \Sup`ple*men"ta*ry\, a. [Cf. F. suppl['e]mentaire.] Added to supply what is wanted; additional; being, or serving as, a supplement; as, a supplemental law; a supplementary sheet or volume.

Supplemental air (Physiol.), the air which in addition to the residual air remains in the lungs after ordinary expiration, but which, unlike the residual air, can be expelled; reserve air.

Supplemental bill (Equity), a bill filed in aid of an original bill to supply some deffect in the latter, or to set forth new facts which can not be done by amendment.
--Burrill.
--Daniel.

Supplementary chords (Math.), in an ellipse or hyperbola, any two chords drawn through the extremities of a diameter, and intersecting on the curve.