- cos 720+tg 30-ctg 210+sin 120

-сos720+tg30-ctg210+sin120=-cos0+tg30-ctg(270-60)+sin(180-60)==-1+1/√3+tg60+sin60=-1+√3/3+√3+√3/2=(-6+2√3+6√3+3√3)/6=(-6+11√3)/6