Question

prove that cosx+cos(2π/x)+cos(2π/3-x)=o

Answer 1

Hey.
As you asked in inbox question should be:-
prove that cosx+cos(2π/3+ x)+cos(2π/3-x)=0
....in second step!..................we know that
cosC + cosD = 2cos(Ç+D)/2 + cos(C-D)/2.
see picture!!
Hope it helped you!!