COS (Number) COS (Number) Number Number Number The angle in radians. Returns Number Number The trigonometric cosine. Details Returns the trigonometric cosine of an angle. The result is in the range -1 to 1. Use RADIANS to convert an angle from degrees to radians before passing it to this function. The inverse of this function is ACOS. Example COS ( RADIANS (60)) COS ( RADIANS (60)) Returns 0.5.