4.11 2 cos(π/2 - α) sin(π/2 + α) tg(π - α)

cos(π/2 - α) = sin(α); sin(π/2 + α) = cos(α); tg(π - α) = -tg(α). 2 * sin(α) * cos(α) * (-tg(α)) = -2 * sin(α) * cos(α) * (sin(α)/cos(α)) = -2sin²(α)