Q23 / 105 · NTA Abhyas (JEE Main) 2020 · Mathematics · Circle

Tangents are drawn to a unit circle with centre at the origin from each point on the line x+y=2. Then, the area (in sq. units) of the locus of the mid-point of the chord of contact is

  • A
    π4
  • B
    π16
  • Correct answer
    C
    π8
  • D
    2π8

Solution

x1,y1 lies on x+y=2
⇒x1+y1=2…i
Chord of contact with respect to x1,y1
xx1+yy1=1
Figure
Also equation of chord whose mid point is h,k
h2+k2=hx+ky
∴x1h=y1k=1h2+k2
⇒x1=hh2+k2, y1=kh2+k2
Substituting in i, we get,
hh2+k2+kh2+k2=2
Hence, the required locus is x2+y2=x2+y2

The area of the circle is π 8  sq. units

Hence, the correct answer is option: 'C'.

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