Hyperbolic Tangent of Sum/Corollary

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Corollary to Hyperbolic Tangent of Sum

$\map \tanh {a - b} = \dfrac {\tanh a - \tanh b} {1 - \tanh a \tanh b}$

where $\tanh$ denotes the hyperbolic tangent.


Proof

\(\ds \map \tanh {a - b}\) \(=\) \(\ds \frac {\tanh a + \map \tanh {-b} } {1 + \tanh a \, \map \tanh {-b} }\) Hyperbolic Tangent of Sum
\(\ds \) \(=\) \(\ds \frac {\tanh a - \tanh b} {1 - \tanh a \tanh b}\) Hyperbolic Tangent Function is Odd

$\blacksquare$


Sources