Question

Costeeta+cos(120dgree+teeta)+cos(120dgree+teeta)=0

Answer 1

Answer:

$cos\theta + cos(120^0 +\theta) +cos(120^0-\theta)=0$

Step-by-step explanation:

$cos\theta + cos(120^0 +\theta) +cos(120^0-\theta)\\cos\theta+(cos120^0cos\theta-sin120^0sin\theta)+(cos120^0cos\theta+sin120^0sin\theta)\\cos\theta+2cos120^0cos\theta\\cos\theta-cos\theta\\0\\since\\cos(A+B)=cosAcosB-sinAsinB\\cos(A-B)=cosAcosB+sinAsinB\\cos120^0=\frac{-1}{2}$

Hope It Helps