cos(L+П/3)+cos(П/3-L)

Question

cos(L+П/3)+cos(П/3-L)

Answer 1

cos(L+П/3)+cos(П/3-L)= cosLcosП/3 - sinLsinП/3 + cosП/3cosL + sinП/3sinL =

= 2 cosL 1/2 = cosL