Question Number 28168 by abdo imad last updated on 21/Jan/18
$${find}\:{the}\:{nature}\:{of}\:\:\sum_{{n}=\mathrm{1}} ^{\infty} {arcos}\left(\mathrm{1}−\frac{\mathrm{1}}{{n}^{{a}} }\right){z}^{{n}} \:\:{with}\:{a}>\mathrm{1}. \\ $$
find-the-nature-of-n-1-arcos-1-1-n-a-z-n-with-a-gt-1-