If `x*costheta=y*cos(theta+(2pi)/3)=2.cos(theta+(4pi)/3)` ,then evaluate `xy+yz+zx`.

If x*cos theta=y*cos(theta+(2 pi)/(3))=2*cos(theta+(4 pi)/(3)) then evaluate xy+yz+zx

If x cos theta=y cos(theta+(2 pi)/(3))=z cos(theta+(4 pi)/(3)), prove that xy+yz+zx=0

If x cos theta=y cos(theta+(2 pi)/(3))=z cos(theta+(4 pi)/(3)), then write the value of (1)/(x)+(1)/(y)=(1)/(z)

If (x)/(cos theta)=(y)/(cos(theta-(2pi)/(2)))=(2)/(cos(theta+(2pi)/(3))), then x+y+z=

If (x)/(cos theta)=(y)/(cos(theta-(2 pi)/(3)))=(z)/(cos(theta+(2 pi)/(3))) then x+y+z is (a)1(b)0(c)-1(d) none of these

If (a/costheta)=(b/(cos(theta+(2pi/3)))=(c/cos(theta+(4pi/3))) then find angle between vectors ahati+bhatj+chatk and bhati+chatj+ahatk if (theta= (2pi/9)) and a^2+b^2+c^2=1 , is

If x=ycos((2pi)/(3))=zcos((4pi)/(3)) ,then what is xy + yz + zx equal to ?

If frac {x}{cos theta} = frac {y}{cos(theta -2pi/3)} = frac {z}{cos(theta +2pi/3)} then x + y + z is equal to

Prove that: cos^3theta+cos^3 (theta- (2pi)/n)+cos^3 (theta- (4pi)/n)+… to n terms =0