Правильно.
2cos840°-√48*sin600°+ctg²30° =2*cos(840-2*360) - √48*sin(600-360) + (√3)^2= 4*cos(120) -√48 * sin 240 + 3 = 2* (-cos 60) -√48 * sin (180 + 60) +3 = -2*0,5 + √48*(√3/2) + 3 = -1 + (√144/2) + 3 = -1 + 12/2 + 3 = -1 + 6 + 3 = 7
