2) <span>-2 3/4 +(+ 6,8) + (- 1,25) + (+ 3 1/5) = -2 3/4 + 6,8 - 1,25 + 3 1/5 = -2 3/4 + 6 8/10 - 1 1/4 + 3 1/5 = -11/4 + 68/10 - 5/4 + 16/5 = -55/20 + 136/20 - 25/20 + 64/20 = 120/20 = 6
3) </span><span>- 5 1/6 + (+ 7 1/9) + (-4 1/3) + (-7 1/9) = -5 1/6 + 7 1/9 - 4 1/3 - 7 1/9 = -31/6 + 64/9 - 13/3 - 64/9 = -31/6 - 13/3 = -31/6 - 26/6 = -57/6 = -9 3/6 = -9 1/2
</span>
5 1/8=5+1/8
7 5/18=7+5/18
12 13/75=12+13/75
8 11/39=8+11/39
Надеюсь правельно...................
18(5а+4b+с) вот я упростил
Согласно формулам привдения 1) cos 5*π/6 = - cos (π - 5*π/6) = - cos π/6 = - √ 3 / 22) sin (-7*π/4) = sin (-7*π/4 + 2*π) = sin π/4 = √ 2 / 23) tg 11*π/3 = tg(11*π/3 - 4*π) = tg (-π/3) = - tg π/3 = - √ 3<span>4) ctg (-3,5*π) = ctg (-3,5*π + 4*π) = ctg π/2 = 0</span>