`cosA + cos (A + 120) + cos (120 - A) = 0`

cos A + cos (120 ^ (@) + A) + cos (120 ^ (@) - A) =

cos (120^(@)) is -

" cos x + cos " (120^(@) -x ) + " cos "(120^(@) +x)=0

cosA+cos(240^(@)+A)+cos(240^(@)-A)=?

cos120^(@)=

cos ^(2) alpha + cos ^(2) (alpha + 120^(@)) + cos ^(2) (alpha - 120^(@)) is equal to

(cos (45 ^ (@) + A) -cos (45 ^ (@) - A)) / (sin (120 ^ (@) + A) -sin (120 ^ (@) - A)) =

Prove that · (cos 135^@ - cos 120^@)/(cos 135^@ +cos 120^@) = 3-2sqrt2

Prove the following: (i) "sin" alpha+"sin"(alpha+(2pi)/(3))+"sin"(alpha+(4pi)/(3))=0 (ii) cos A+cos(120^(@)-A)+cos(120^(@)+A)=0 .

Prove that cos(120^@-A)+cosA+cos(120^@+A)=0 .