Hyperbolic Sine of Complex Number/Proof 1
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Theorem
Let $a$ and $b$ be real numbers.
Let $i$ be the imaginary unit.
Then:
- $\sinh \paren {a + b i} = \sinh a \cos b + i \cosh a \sin b$
where:
- $\sin$ denotes the real sine function
- $\cos$ denotes the real cosine function
- $\sinh$ denotes the hyperbolic sine function
- $\cosh$ denotes the hyperbolic cosine function.
Proof
\(\ds \sinh \paren {a + b i}\) | \(=\) | \(\ds \sinh a \cosh \paren {b i} + \cosh a \sinh \paren {b i}\) | Hyperbolic Sine of Sum | |||||||||||
\(\ds \) | \(=\) | \(\ds \sinh a \cos b + \cosh a \sin \paren {b i}\) | Cosine in terms of Hyperbolic Cosine | |||||||||||
\(\ds \) | \(=\) | \(\ds \sinh a \cos b + i \cosh a \sin b\) | Sine in terms of Hyperbolic Sine |
$\blacksquare$