Question

Найти значения выражения 1)cos 135° 2) sin 8π/3 3) tg 7π/3 4) cos²π/8-sin²π8

Answer 1

1)cos 135°=cos(180-45)=-cos45=-√2/2
2) sin 8π/3=sin(3π-π/3)=sinπ/3=√3/2
3) tg 7π/3=tg(2π+π/3)=tgπ/3=√3
4) cos²π/8-sin²π8=cosπ/4=√2/2