If a line y = m x + c , is a tangent to the circle x - 3 2 + y 2 = 1 , and it is perpendicular to a line L 1…

If a line y=mx+c, is a tangent to the circle x-32+y2=1, and it is perpendicular to a line L1, where L1 is the tangent to the circle x2+y2=1, at the point 12,12, then
  1. c2-7c+6=0
  2. c2+7c+6=0
  3. c2+6c+7=0
  4. c2-6c+7=0

Solution

Slope of tangent to x2+y2=1 at 12,12
x2+y2=1
2x+2yy'=0
y'=-xy=-1
Given that, y=mx+c, is perpendicular to L1,
So, m=1 y=x+c

Now distance of 3,0 from y=x+c is
c+32=1
c2+6c+9=2
c2+6c+7=0.

Asked in: MHT CET Full Test 7

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