cis radians → number

radians — a real.

number — a complex.

cis returns the value of ↓e^{i· ↓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.

(cis 0) → #C(1.0 0.0)

Section 12.1.3.3 (Rule of Float Substitutability)