Question

как найти ctg(-2*pi/3) или sin(2*pi/3)?

Answer 1

$ctg(-frac{2 pi}{3})=-ctg(frac{2 pi}{3})=-ctg(pi - frac{pi}{3})=-(-ctg (frac{pi}{3}))=ctg (frac{pi}{3})=frac{sqrt{3}}{3} \ \ sin (frac{2 pi}{3})= sin (pi - frac{pi}{3})=sin (frac{pi}{3})=frac{sqrt{3}}{2}$