# Chapter 7 - Exponential Functions - 7.9 Hyperbolic Functions - Exercises - Page 384: 3

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#### Work Step by Step

Let $y=\sinh x$; then $y'=\cosh x$. Since $\cosh x$ is always positive, then $y=\sinh x$ is always increasing. Now, Let $y=\cosh x$, then $y'=\sinh x$. Since $\sin x=0$ at $x=0$, then we have a critical point $x=0$. Since, $\sinh 1\gt 0$, then $y=\cosh x$ is always increasing for all positive values of $x$ and decreasing for all negative values of $x$.

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