Question Number 148768 by mim24 last updated on 31/Jul/21

Answered by liberty last updated on 31/Jul/21

((1−cos (120°+2A)+1−cos 2A+1−cos (120°−2A))/2) = ((3−cos 2A−{cos (120°+2A)+cos (120°−2A)})/2)= ((3−cos 2A−{2cos 120°cos 2A})/2)= ((3−cos 2A−{−cos 2A})/2)=(3/2)