= 1 Let the point P(5‌cos‌θ,4‌sin‌θ) on ellipse then the equation of tangent to ellipse is, x(
cos‌θ
5
)+y(
sin‌θ
4
)=1 ....(I) So, the point Q is Q(
5
cos‌θ
,0) and point R is R(0,5‌sec‌θ) The equation of the circle with QR as diameter is, x(x−5‌sec‌θ)+y(y−5‌sec‌θ)=0 x2+y2−(5‌sec‌θ)x−(5‌sec‌θ)y=0 The above circle passes through the origin.