cos (π(4x+120)/4) = - √2/2
π(x+30) = ± arccos (-√2/2) + 2πn n ∈ Z
π(x+30) = ± 3π/4 + 2πn n ∈ Z
πx = ± 3π/4 - 30π + 2πn n ∈ Z
x = ± 3/4 - 30 + 2n n ∈ Z
x₁ = 3/4 - 30 + 2n = (3 - 120 +8n)/4 = (8n - 117)/4 n ∈ Z
x₂ = -3/4 - 30 + 2n = (-3 - 120 +8n)/4 = (8n - 123)/4 n ∈ Z
1.8n - 117 < 0
n < 117/8
n = 14
x₁ = (8*14 - 117)/4 = - 5/4
2. 8n - 123 < 0
n < 123/8
n = 15
x₂ = (8*15 - 123)/4 = - 3/4
x₂ > x₁
ответ -3/4
cos (π(4x+120)/4) = - √2/2
π(x+30) = ± arccos (-√2/2) + 2πn n ∈ Z
π(x+30) = ± 3π/4 + 2πn n ∈ Z
πx = ± 3π/4 - 30π + 2πn n ∈ Z
x = ± 3/4 - 30 + 2n n ∈ Z
x₁ = 3/4 - 30 + 2n = (3 - 120 +8n)/4 = (8n - 117)/4 n ∈ Z
x₂ = -3/4 - 30 + 2n = (-3 - 120 +8n)/4 = (8n - 123)/4 n ∈ Z
1.8n - 117 < 0
n < 117/8
n = 14
x₁ = (8*14 - 117)/4 = - 5/4
2. 8n - 123 < 0
n < 123/8
n = 15
x₂ = (8*15 - 123)/4 = - 3/4
x₂ > x₁
ответ -3/4