cos
The trigonometric cosine function.
Syntax

cos(x)

x
is a real or complex number

Description
If x
is a real number, cos(x)
is the x
coordinate of the intersection of the unit circle x^2 + y^2 = 1
and the ray from the origin making an angle x
(in radians) from the positive x
axis in the anticlockwise direction.
If z
is a complex number, cos(z)
is defined as [e^(i⋅z) + e^(−i⋅z)]/2
.
Notes
If you want to specify the argument in degrees, you can use the ° postfix operator, which amounts to multiplication by π/180.
Examples
cos(0)
1
cos(π/2)
0
cos(180°)
−1
cos(i)
1.54308063482