Sine in terms of Hyperbolic Sine

Theorem

 * $\sinh \left({ix}\right) = i \sin x $

where $\sin$ is the sine, $\sinh$ is the hyperbolic sine, and $i^2=-1$.

Also see

 * Hyperbolic Cosine of Imaginary Number
 * Hyperbolic Tangent of Imaginary Number
 * Hyperbolic Cotangent of Imaginary Number
 * Hyperbolic Secant of Imaginary Number
 * Hyperbolic Cosecant of Imaginary Number