`cos theta + cos (120^(@) + theta ) + cos (120^(@) - theta )=`

cos^(3) theta + cos^(3) ( 120^(@) +theta ) + cos^(3) (120^(@) - theta )=

If cot theta = 8//15 and theta does not lie in the first quadrant , then cos (30^(@) + theta ) + sin (45^(@) - theta ) + cos(120^(@) + theta ) =

I : If x cos theta = y cos (120^@ + theta ) = z cos ( theta + 240^(@)) then xy+ yz+ zx=1 II : cos alpha + cos (120^(@) + alpha ) + cos (120^@ - alpha ) =0

Show that cos theta+cos(120^(@)+theta)+cos(240^(@)+theta)=0

If theta + phi = 60^(@) , show that, sin (120^(@) - theta) = cos (30^(@) - phi) .