COS X + COS (120° - x) + cos (120° + x) = 0
Answers
Answer:
LHS=RHS
Step-by-step explanation:
LHS = cosx+cos(120°-x)+cos(120°+x)
(120°-x=C,120°+x=D
cosC+cosD = 2cos(C+D)/2*cos(C+D)/2)
cosx+2cos(120°-x+120°+x) cos(120°-x-120°-x).
2. 2
=cosx+2 cos 120 cos(-x)
( cos(-theta)= cos theta)
= cosx+2cos120 cosx
(cos 120°= cos(180-60)
=-cos 60
=-1/2)
= cosx+2*-1/2*cos x
= cosx-cosx
=0 =RHS