4.8 (sin 150° - cos 240°) / (ctg 730° ctg 800° + tg 730° tg 800°)

sin(150°) = 1/2; cos(240°) = -1/2; ctg(730°) = ctg(730°-2*360°) = ctg(10°) ; ctg(800°) = ctg(800°-2*360°) = ctg(80°); tg(730°) = tg(730°-2*360°) = tg(10°); tg(800°) = tg(800°-2*360°) = tg(80°). (1/2 - (-1/2)) / (ctg(10°) ctg(80°) + tg(10°) tg(80°)) = 1 / (ctg(10°) * ctg(90°-10°) + tg(10°) * tg(90°-10°)) = 1 / (ctg(10°) * tg(10°) + tg(10°) * ctg(10°)) = 1 / (1 + 1) = 1/2