The locus of the mid points of the chords of the circle $C_1:(x-4)^2+(y-5)^2=4$ which subtend an angle $\theta_i$ at the centre of the circle $C_1$, is a circle of radius $r_i$. If $\theta_1=\frac{\pi}{3}, \theta_3=\frac{2 \pi}{3}$ and $r_1^2=r_2^2+r_3^2$, then $\theta_2$ is equal to
$\frac{\pi}{4}$
$\frac{3 \pi}{4}$
$\frac{\pi}{6}$
$\frac{\pi}{2}$
The radical centre of three circles described on the three sides of a triangle as diameter is
In the co-axial system of circle ${x^2} + {y^2} + 2gx + c = 0$, where $g$ is a parameter, if $c > 0$ then the circles are
Figure shows $\Delta ABC$ with $AB = 3, AC = 4$ & $BC = 5$. Three circles $S_1, S_2$ & $S_3$ have their centres on $A, B $ & $C$ respectively and they externally touches each other. The sum of areas of three circles is
The equation of the circle having its centre on the line $x + 2y - 3 = 0$ and passing through the points of intersection of the circles ${x^2} + {y^2} - 2x - 4y + 1 = 0$ and ${x^2} + {y^2} - 4x - 2y + 4 = 0$, is
The value of k so that ${x^2} + {y^2} + kx + 4y + 2 = 0$ and $2({x^2} + {y^2}) - 4x - 3y + k = 0$ cut orthogonally is