cos ( - П \ 3) + cos ( - П \ 6) + cos ( - П \ 2) + cos ( 2П ) = ?

Question

cos ( - П \ 3) + cos ( - П \ 6) + cos ( - П \ 2) + cos ( 2П ) = ?

Answer 1

cos(-π/3)+cos(-π/6)+cos(-π/2)+cos(2π)=1/2+√3/2+0+1=(3+√3)/2=√3(√3+1)/2.