Question

Find the equation of the chord of contact of the tangents drawn from (1, 2) to the circle $x^2+y^2-2x+4y+7=0$

Answer 1

The given equation of circle is,

$x^2+y^2-2x+4y+7=0$

Let $P=\left(1,2\right)$. So, the equation of circle for the point $\left(x_1,y_1\right)$ is,

$x{x}_1+y{y}_1+g\left(x+x_1\right)+h\left(y+y_1\right)-r=0$

$x\left(1\right)+y\left(2\right)-2\left(x+1\right)+4\left(y+2\right)+7=0$

$x-6y+13=0$