sin(-\frac{5}{3}\pi)
źródło:
sin(-\frac{5}{3} \pi)=-sin(\frac{5}{3} \pi)=
=-sin(\frac{3}{3}\pi+\frac{2}{3}\pi)=-sin(\pi+\frac{2}{3}\pi)=
=sin(\frac{2}{3}\pi)=sin(\frac{1}{2}\pi +\frac{1}{6}\pi)=
=cos(\frac{1}{6}\pi)=\frac{\sqrt3}{2}