Question

Tangents $PA$ and $PB$ are drawn to $x^2+y^2=a^2$ from the point $P(x_1,y_1)$. Then find the equation of the circumcircle of triangle $PAB$.

Answer 1

Since the circumcircle of $△PAB$ will have the diameter joining $P$ and centre of the circle

$x^2+y^2=a^2$ i.e., $(0,0)$

Therefore, the equation of the circumcircle $\left[x\right(x-y)+y(y-y_1\left)\right]$