I got you covered. There are two ways to write Θ: degrees [°] and radians [expressed as "π"]. So, in this case cos π/3 = ½ [radian measure], or cos 60° = ½ [degree measure]. The reason being is because to convert from degrees to radians, use this formula: [degree measure] π/180; if you were to convert from radians to degrees, you'd do this vice versa: [radian measure] 180/π. So basically, the unit you're trying to convert to, is the one that goes in your numerator.