263. \(F_1, F_2\) are left and right focus points of the hyperbola \(C : \dfrac{x^2}{a^2} - \dfrac{y^2}{b^2} = 1\) \((a > 0, b > 0)\). Point \(O\) is the origin of the coordinate, \(M\) is an arbitrary point on \(C\) and above the \(x\)-axis. \(H\) is a point of \(MF_1\). Given that \(MF_2 \perp F_1F_2\), \(MF_1 \perp OH\), \(|OH| = \lambda|OF_2|\), where \(\lambda \in \left(\dfrac{1}{3}, \dfrac{1}{2}\right)\). Find the range of the eccentricity of the hyperbola \(C\).
If \(P(x_1, y_1)\), \(Q(x_2, y_2)\), \(R(x_3, y_3)\) and \(S(x_4, y_4)\) are four concyclic points on the rectangular hyperbola \(xy = c^2\), then coordinates of the orthocentre of the \(\triangle PQR\) are
For some $\theta\in\left(0,\dfrac{\pi}{2}\right)$, let the eccentricity and the length of the latus rectum of the hyperbola $x^2-y^2\sec^2\theta=8$ be $e_1$ and $l_1$, respectively, and let the eccentricity and the length of the latus rectum of the ellipse $x^2\sec^2\theta+y^2=6$ be $e_2$ and $l_2$, respectively. If $e_1^2=e_2^2(\sec^2\theta+1)$, then $\left(\dfrac{l_1 l_2}{e_1 e_2}\right)\tan^2\theta$ is equal to _____.