Сравни числа с помощью единичной окружности

1. \(\cos \dfrac{2\pi}{3}\) [ \(\gt\) | \(\lt\) | \(=\) ] \(\cos \dfrac{5\pi}{6}\) ;

2. \(\cos \dfrac{3\pi}{4}\) [ \(\gt\) | \(\lt\) | \(=\) ] \(\cos \dfrac{5\pi}{8}\) .