### Complex sine

The **complex sine** can be expressed with exponential functions as

##### Explanation

We start with the power series for the complex sine

and multiply all terms with 2*i* and get

By conversion with the imaginary unit all terms obtain a plus sign

You can also write it as

We add even exponents and subtract these immediately

Rearranging gives

In brackets are two power series for exponential functions, and thus

so that

##### Example 1

You can see that sin (0) = 0, as

## HistoryThis formula for the sine was described by the Swiss mathematician Leonhard Euler (1707 - 1783). |