Combined equation of pair of lines through the origin joining the points of intersection of lien y=√mx+1 with the given curve is x2+2xy+(2+sinα)y2−(y−mx)2=0 for the chord to subtend a right angle at the origin (1−m)+(2+sin2α−1)=0 (as sum of the coefficient of x2+y2=0) ⇒sin2α=m−2 ⇒0≤m−2≤1 ⇒2≤m≤3