Q.

Let the ellipse E:x2+9y2=9 intersect the positive x- and y-axes at the points A and B respectively. Let the major axis of E be a diameter of the circle C. Let the line passing through A and B meet the circle C at the point P. If the area of the triangle with vertices A, P and the origin O is mn, where m and n are coprime, then m-n is equal to              [2023]

1 17  
2 15  
3 18  
4 16  

Ans.

(1)

We have, E:x29+y21=1

      A(3,0)

      B(0,1)

Equation of line passing through A(3, 0) and B(0, 1) is y-0x-3=1-00-3  x+3y=3               ...(i)

The equation of the circle with radius 3 is x2+y2=9                      ...(ii)

From (i) and (ii), we get
     (3-3y)2+y2=910y2-18y=0y=0,95

   Area of triangle OPA=12×3×95=2710=mn

  m-n=17