If a line, y = mx + c is a tangent to the circle, (x – 3)2 + y2 = 1 and it is perpendicular to a line L1, where L1 is the tangent to the circle, x2 + y2 = 1 at the point $\left( {{1 \over {\sqrt 2 }},{1 \over {\sqrt 2 }}} \right)$, then :
Solution
For circle x<sup>2</sup> + y<sup>2</sup>
= 1 tangnet at point P$\left( {{1 \over {\sqrt 2 }},{1 \over {\sqrt 2 }}} \right)$ is
<br><br>T = 0
<br><br>$\Rightarrow$ ${1 \over {\sqrt 2 }}x + {1 \over {\sqrt 2 }}y - 1 = 0$
<br><br>$\Rightarrow$ x + y - $\sqrt 2$ = 0
<br><br>Perpendicular to the line is
<br><br>x - y + c = 0
<br><br>This is tangent to the circle (x – 3)<sup>2</sup>
+ y<sup>2</sup>
= 1
<br><br>Also we know, perpendicular distance from center = radius
<br><br>$\therefore$ $\left| {{{3 - 0 + c} \over {\sqrt 2 }}} \right|$ = 1
<br><br>$\Rightarrow$ |3 + c| = ${\sqrt 2 }$
<br><br>$\Rightarrow$ ${\left( {3 + c} \right)^2} = 2$
<br><br>$\Rightarrow$ 9 + c<sup>2</sup>
+ 6c = 2
<br><br>$\Rightarrow$ c<sup>2</sup>
+ 6c + 7 = 0
About this question
Subject: Mathematics · Chapter: Circles · Topic: Equation of a Circle
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