Определите знак выражения
cos[tex]\frac{5\pi }{7}[/tex] + cos[tex]\frac{3\pi }{4}[/tex]

cos5π/7+cos3π/4 ??cos(π-2π/7)+cos(π-π/4)=-cos(2π/7)-cos(π/4)=-(cos2π/7+cosπ/4)<0(cos(2π/7)>0;cos(π/4)>0)(cos5π/7+cos3π/4)<0