А) Sin865°= Sin(90°*9 + 55°)= Cos55°
tg31π/4 = tg(8π - π/4) =- tgπ/4= -1
Sin11π/3 + Cos19π/3 =Sin(4π - π/3) + Cos(6π + π/3) = -Sinπ/3 + Cosπ/3 =
=-√3/2 + 1/2
б) Sin(13π -x) + Cos(5π/2+x) = Sinx -Sinx = 0
Sin²3π/2 + Cos²(5π - x) = 1 + Cos²x
tg(3π -x) tg(5π/2 +x) = -tgx*(-Ctgx) = 1