Вот решение...................
1.
2cos²α-8sin²α=2(1-sin²α)-8sin²α=2-2sin²α-8sin²α=2-10sin²α
2-10*(0.3)²=2-10*0.09=2-0.9=1.1
2.
3.
x∈[-0.5; +∞)
Cos(3x - π/2) = 1/2
sin3x = 1/2
3x = (-1)^n*arcsin(1/2) + πk,k∈Z
3x = (-1)^(n)(π/6) + πk, k∈z
x = (-1)^(n)(π/18) +πk/3, n∈Z
1 - 12y < 3y + 1
3y + 12y > 1 - 1
15y > 0
y > 0
( 0 ; + бесконечность )