cos
Function 
cos(angle)

cos is included by default in each file as part of the Math library.
See also:
Use
The Cos() function returns the cosine of an angle. The input must have an angular unit, but unitless is acceptable and will be treated as radians.
Cos() works with complex numbers.
Examples of trig functions
Cos(0.5) = 0.878
Cos(0.5 rad) = 0.878
Sin(45 deg) = 0.707
Tan(1 + i) = 0.272 + 1.0839i
Tan((60 + 30i) deg) = 0.787 + 1.135i