(Solved): 2. The hyperbolic sine and cosine functions are defined as \\[ \\sinh (x)=\\frac{e^{x}-e^{-x}}{2}, ...

2. The hyperbolic sine and cosine functions are defined as \\[ \\sinh (x)=\\frac{e^{x}-e^{-x}}{2}, \\cosh (x)=\\frac{e^{x}+e^{-x}}{2} \\] Identify which values of \\( k \\) make \\( \\sinh (k x) \\) a solution to \\[ y^{\\prime \\prime}-9 y=0 \\]