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1)

The radius of a circle having minimum area, which touches the curve y=4-x2 and the line y=|x| , is


A) 2(2+1)

B) 2(21)

C) 4(21)

D) 4(2+1)

Answer:

Option C

Explanation:

Let the radius circle with least area be r

                  Then, then coordinates of centre= (0,4,-r)

      29112019150_circle.PNG

Since, circle touches the line y=x in first quadrant

       

                        0(4r)2∣=r

    r4=±r2

         r=42+1   or   412

But                    r412        [412<0]

        r=42+1=4(21)