A complex number z is defined by z = (1/2)(cos θ + isin θ),such that
z^n = (1/2^n ) (cos nθ + isin nθ)
Using De Moivre′s theorem,or otherwise, show that
(i) Σ_(r=0) ^∞ (1/4^r ) sin 2rθ is a convergent geometic progression.
(ii) Σ_(r=0) ^∞ (1/4^r ) sin 2r = ((14 sin 2θ)/(17−16cos 2θ))
|