Не решить ? найдите cos8 α − sin8 α, если cos2 α = m.

Cos⁸(a) - sin⁸(a) = (cos²(a))⁴ - (sin²(a))⁴ = m⁴ - (1 - cos²(a))⁴ = m⁴ - (1 - m)⁴ = 
= (m² - (1-m)²)(m² + (1-m)²) = (m²-1+2m-m²)(m²+1-2m+m²) = 
= (2m - 1)(2m² - 2m + 1) = 4m³ - 6m² + 4m - 1