The angle subtended at the origin by the common chord of the circles $x^2 + y^2 - 6x - 6y = 0$ and $x^2 + y^2 = 36$ is (A) $\pi/2$ (B) $\pi/4$ (C) $\pi/3$ (D) $2\pi/3$
The angle subtended at the origin by the common chord of the circles $x^2 + y^2 - 6x - 6y = 0$ and $x^2 + y^2 = 36$ is\\
(A) $\pi/2$\\
(B) $\pi/4$\\
(C) $\pi/3$\\
(D) $2\pi/3$