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Section 4.3 Hyperbolics

Subsection 4.3.1 Definitions

\begin{align*} \amp \sinh x \amp = \dfrac{e^x - e^{-x}}{2} \\ \amp \cosh x \amp = \dfrac{e^x + e^{-x}}{2} \end{align*}

Subsection 4.3.2 Basic Identities

\begin{align*} \cosh^2 - \sinh^2 \amp = 1\\ \tanh^2 x \amp = 1 - \sech^2 x\\ \coth^2 x \amp = 1 + \csch^2 x \end{align*}

Subsection 4.3.3 Additions

\begin{align*} \sinh (x + y) \amp = \sinh x \cosh y + \cosh x \sinh y \\ \cosh (x + y) \amp = \cosh x \cosh y + \sinh x \sinh y \\ \tanh (x + y) \amp = \dfrac{\tanh x + \tanh y}{1 + \tanh x \tanh y} \end{align*}

Subsection 4.3.4 Subtractions

\begin{align*} \sinh (x - y) \amp = \sinh x \cosh y - \cosh x \sinh y \\ \cosh (x - y) \amp = \cosh x \cosh y - \sinh x \sinh y \\ \tanh (x - y) \amp = \dfrac{\tanh x - \tanh y}{1 - \tanh x \tanh y} \end{align*}

Subsection 4.3.5 Double Angles

\begin{align*} \sinh 2x \amp = 2 \sinh x \cosh x \\ \cosh 2x \amp = \cosh^2 x + \sinh^2 x \end{align*}

Subsection 4.3.6 Half Angles

\begin{align*} \sinh^2 x \amp = \dfrac{\cosh 2x - 1}{2} \\ \cosh^2 x \amp = \dfrac{ \cosh 2x + 1}{2} \end{align*}

Subsection 4.3.7 Inverse Hyperbolic Functions

\begin{align*} \amp \text{Function} \amp \amp \text{Domain} \amp \amp \text{Range} \amp \amp \text{Inverse} \\ \amp \sinh x \amp \amp \RR \amp \amp \RR \amp \amp \arcsinh x\\ \amp \cosh x \amp \amp [0, \infty) \amp \amp [1,\infty) \amp \amp \arccosh x \\ \amp \tanh x \amp \amp \RR \amp \amp (-1,1) \amp \amp \arctanh x \\ \amp \sech x \amp \amp \left[ 0, \infty \right) \amp \amp (0,1] \amp\amp \arcsech x\\ \amp \csch x \amp \amp (-\infty,0) \cup (0, \infty) \amp \amp (-\infty,0) \cup (0, \infty) \amp \amp \arccsch x \\ \amp \coth x \amp \amp (-\infty,0) \cup (0, \infty) \amp \amp (-\infty,1) \cup (1,\infty) \amp \amp \arccoth x \end{align*}