Разбираемся:
2 sin(α - 3π) - cos(-π/2 + α) = 2 sin(α - 3π) - cos(α - π/2) = -2 sin(3π - α) - sin(α) = -2 (-sin(π - α)) - sin(α) = 2sin(α) - sin(α) = sin(α)
5 sin(α - π) = -5 sin(π - α) = -5 sin(α)
\(\frac{sin(α)}{-5 sin(α)} = -\frac{1}{5}\)
Ответ: -\(\frac{1}{5}\)