  Translated from the Latin original, "Observationes generales circa series,
quarum termini secundum sinus vel cosinus angulorum multiplorum progrediuntur"
(1777). E655 in the Enestrom index. Euler looks at the binomial expansion
$(1+x)^n$ for $x=\cos \phi+i\sin\phi$. He does $n=$ positive and negative
integers, and $n={1/2}, -{1/2}$, and particular values of $\phi$.
