1 дм= 10 см
следовательно 10 больше 9 см 9 мм т.к 10 уже больше 9
→ →
АВ{-8, 10, -8}, |AB| = √(64 + 100 + 64) = √228= 2√57
→ →
CD{-2, 8, 12}, | CD| = √ (4 + 64 +144)=√212 = 2√53
Cosα = (16 +80 - 96)/(2√57*2√53) = 0
α = 90°
<span>сtg(3x - π/6) = √3
3x - </span>π/6 = arcctg√3 + πn, n ∈ Z
3x - π/6 = π/6 + πn, n ∈ Z
3x = 2π/6 + πn, n ∈ z
3x = π/3 + πn, n ∈ Z
x = π/9 + πn/3, n ∈ Z
Отберем корни, принадлежащие отрезку <span>[-5π/2; -2π].
</span>при n = 0 х= π/9 ∉ <span>[-5π/2; -2π],
</span>при n = -1 х= π/9 - π/3 = π/9 - 3π/9 = -2π/9 ∉ <span>[-5π/2; -2π],
</span>при n = -2 х= π/9 - 2π/3 = π/9 - 6π/9 = -5π/9 ∉ <span>[-5π/2; -2π],
</span>при n = -3 х= π/9 - 3π/3 = π/9 - π = -8π/9 ∉ [-5π/2; -2π],
при n = -4 х= π/9 - 4π/3 =π/9 - 12π/9 = -11π/9 ∉ [-5π/2; -2π],
при n = -5 х= π/9 - 5π/3 = π/9 - 15π/9 = -14π/9 ∉ [-5π/2; -2π],
при n = -6 х= π/9 - 6π/3 = π/9 - 2π = -17π/9 ∉ [-5π/2; -2π],
при n = -7 х= π/9 - 7π/3 = π/9 - 21π/9 = -20π/9<span> </span>∈ [-5π/2; -2π],
при n = -8 х= π/9 - 8π/3 = π/9 - 24π/9 = -23π/9 ∉ [-5π/2; -2π],
<span>
</span>Ответ: -20π/9.