15.8.2.7 Math.cos(x)

number Math.cos(x:radian|mixed)

Return to cosine of x.

Math.cos = function(x){
x = ToNumber(x);
if (isNaN(x)) return NaN;
if (x === +0) return 1;
if (x === -0) return 1;
if (x === +Infinity) return NaN;
if (x === -Infinity) return NaN;
return Math.cos(x);
}