Return the cosine of {expr}, measured in radians, as a |Float|. {expr} must evaluate to a |Float| or a |Number|. Returns 0.0 if {expr} is not a |Float| or a |Number|. Examples: :echo cos(100) 0.862319 :echo cos(-4.01) -0.646043 Can also be used as a |method|: Compute()->cos() {only available when compiled with the |+float| feature}