Tg240° = tg(270° - 30°) = ctg30° = √3
ctg225° = ctg(270° - 45°) = tg45° = 1
tg240° * ctg225° = √3
sin2x = 2sinxcosx
6sin75° * cos75° = 3 * (2sin75°cos75°) = 3 * sin(2 * 75°) = 3sin150° = 3sin(180° - 30°) = 3sin30° = 3 * 1/2 = 3/2
6sin75° * cos75° - tg240° * ctg225° = 3/2 - √3