а) 2sin30 - ctg45
sin30 = 1/2
ctg45 = 1/tan45 = 1/1 = 1

2*1/2 - 1 = 1 - 1 = 0

Ответ: 0

б) 4sin45 - cos30 + 8tg60
sin45 = sqrt(2)/2
cos30 = sqrt(3)/2
tg60 = sqrt(3)

4sqrt(2)/2 - sqrt(3)/2 + 8sqrt(3) = 2sqrt(2) - sqrt(3) + 8sqrt(3) = 7sqrt(3) - sqrt(3) = 6sqrt(3)

Ответ: 6sqrt(3)

в) 4ctg30 * cos60
ctg30 = 1/tan30 = sqrt(3)
cos60 = 1/2

4sqrt(3) 1/2 = 2sqrt(3)

Ответ: 2sqrt(3)