## Calculus 8th Edition

$\sinh x= \dfrac{4}{3}$
As we are given that $x \gt 0$, so $\sinh x = \sqrt{ (cosh^{2}x - 1)}$ Plug $\cosh x = \dfrac{5}{3}$ Thus, $\sinh x =\sqrt{ (\frac{5}{3}^{2}-1)}$ or, $=\sqrt {\dfrac{25}{9}-1}$ or, $=\sqrt{ \dfrac{25-9}{9}}$ or, $=\sqrt {\dfrac{16}{9}}$ or, $= \dfrac{4}{3}$