Ctg(-420°)+cos810°-sin(-2,25П)

ctg(-360-60)+cos(720+90)-sin(-2π-π/4)=-ctg60+cos90+sinπ/4=-1/√3+0+√2/2= =(3√2-2√3)/6

[latex]ctg(-420)+cos810-sin(-2,25\pi)=ctg(-60)+cos90-sin(-\frac{\pi}{4})=\\=-\frac{\sqrt3}{3}+0+\frac{\sqrt{2}}{2}=\frac{3\sqrt2-2\sqrt3}{6}=\frac{\sqrt6(\sqrt3-\sqrt2)}{6}=\frac{\sqrt3-\sqrt2}{\sqrt6}[/latex]