Let y = cos/7 cos2/7 cos4/7 ..... y(2sin/7) = (2sin/7cos/7) cos2/7 cos4/7 .....upto n terms y(2sin/7) = sin2/7 cos2/7 cos4/7 .....upto n terms y(22sin/7) = (2sin2/7 cos2/7) cos4/7 .....upto n terms y(22sin/7) = sin4/7 cos4/7 .....upto n terms Similarly y(2nsin/7) = sin2n+1/7 y= sin2n+1/7/2nsin/7 The required sum is S = n y = n sin2n+1/7/2nsin/7 = 0 As the Nr is a bounded quantity lying between -1 and 1. So it has a finite value. The Dr increases without bound. Hence the quotient approaches zero.
Moderation Team
![[Post New]](/templates/default/images/icon_minipost_new.gif){kind=icon}
![[Up]](/templates/default/images/icon_up.gif "[Up]"){kind=icon}
380
/7 cos2
/7 cos4
y = n
