$ \sin h^{-1} 2+ \sin h^{-1}3=x => \cos h\; x=$

Question

\[\begin {array} {1 1} (1)\;\frac{1}{2} (3 \sqrt 5+2 \sqrt {10}) & \quad (2)\;\frac{1}{2}(3\sqrt {5}-2 \sqrt {10}) \\ (3)\;\frac{1}{2} (12+2 \sqrt {50})& \quad (4)\;\frac{1}{2}(12-2 \sqrt {50}) \end {array}\]