I have asked this question before and it helped me get a little further, but not at a solution.
I have to algebraically reduce the expression:
$\sinh(2 \cdot \sinh^{-1}(y))$
Now i had the idea of using the hyperbolic addition formulas, but i got some convoluted answers. The earlier question i asked helped me on the way a bit with this:
$\sinh(2x) = 2 \sinh(x) \cosh(x)$ where $x = \sinh^{-1}(y)$
$= 2 y \cosh(x)$.
Now $\cosh(x) = \sqrt{1 + \sinh(x)^2}$.
But i have no idea of where to go from here. I hope someone can help me. Thanks in advance.