4×cos11<u><em></em></u> ×sin11÷5×
sin 22=
0.0561.....
2Sin 2x Cos 2x = 6Cos² 2x -4(Sin² 2x + Cos²2x)
2Sin 2x Cos 2x - 6Cos² 2x + 4Sin² 2x + 4Cos²2x= 0
2Sin 2x Cos 2x - 2Cos² 2x +4 Sin² 2x = 0 | : Сos²2x ≠ 0
2 tg 2x - 2 +4tg² 2x = 0
2tg² 2x + tg x -1 = 0
решаем как квадратное.
D = 9
tg 2x =( -1 +-3)/4
а) tg 2x = 1/2 б) tg 2x = -1
2x = arctg 1/2 + πk , k∈Z 2x = arctg(-1) + πn, n∈Z
x = 1/2 arctg 1/2 + πk/2 , k∈Z 2x = -π/4 +πn , n ∈Z
x = - π/8 + πn/2 , n ∈Z
(7/2-1/2):3/4-5:(1/3-1/8)=(7/8-4/8):3/4-5:(8/24-3/24)=38/:3/4-5:5/24=3/8*4/3-5*24/5=1,2-24=-23,5