If `alpha=pi/31` then find the value of `1/4[1/(cosalpha)+(2cosalpha)/(cos2alpha)+(4cos3alpha)/(cos4alpha)+(8cos7alpha)/(cos8alpha)]`

If alpha=(pi)/(31) then find the value of (1)/(4)[(1)/(cos alpha)+(2cos alpha)/(cos2 alpha)+(4cos3 alpha)/(cos4 alpha)+(8cos7 alpha)/(cos8 alpha)]

If alpha=pi/7 then find the value of (1/cosalpha+(2cosalpha)/(cos2alpha))

If alpha=pi/7 then find the value of (1/cosalpha+(2cosalpha)/(cos2alpha))

If alpha=(pi)/(7) then find the value of ((1)/(cos alpha)+(2cos alpha)/(cos2 alpha))

If alpha=(pi)/(7), then find the value of ((1)/(cos alpha)+(2cos alpha)/(cos2 alpha))

1/(cosalpha+cos3alpha)+1/(cosalpha+cos5alpha)....1/(cosalpha+cos(2n+1)alpha

cos alpha*cos60-alpha*cos60+alpha-(1)/(4)cos3 alpha

(1)/(cos alpha+cos3 alpha)+(1)/(cos alpha+cos5 alpha)...(.1)/(cos alpha+cos(2n+1)alpha)

(sin 5 alpha-sin3alpha)/(cos 5 alpha+2 cos 4 alpha+cos 3alpha)=

If alpha =(pi)/(18) radian then the value of (cos alpha + cos 2 alpha+ cos 3 alpha +…+ cos 18 alpha) is-