<span>Решаем</span><span>по</span><span>теореме</span><span>синусов</span><span> DE/sin DCE = CE/sin CDE, CE = DE sin CDE/sin DCE = 3</span><em><span>√3</span></em><span /><span>·sin120°/ 0,5 = 3</span><em><span>√3·√3</span></em><span /><span>/2/0,5 = 9</span>
2πr=40 π
10 π=40π/4
Вся окружность равна 360°, четверть = 360°:4=90°