sin 225° = sin(180°+45°) = -sin45° = -√2/2.
cos120° = cos(180°-60°) = -cos60° =-1/2.
tg300° = tg(-60°) = -tg60° = -√3.
tg240° = tg(180°+60°) = tg60° = √3.
4 sin 225° - 6cos 120°+ tg300°+3tg240° =
4*(-√2/2)-6*(-1/2)+(-√3)+3*√3 = -2√2 + 3 + 2√3 ≈ 3.635674.