#### 12.2.45 cis [Function]

`cis` radians ⇒ number

#### Arguments and Values::

radians—a real.

number—a complex.

#### Description::

cis returns the value of~e^i\cdot radians, which is a complex in which the real part is equal to the cosine of radians, and the imaginary part is equal to the sine of radians.

#### Examples::

     (cis 0) ⇒  #C(1.0 0.0)

#### See Also::

Rule of Float Substitutability