3arccosx + 3arccos⁻¹ x + 10 = 0
3arccosx + 3/arccos x + 10 = 0 умножим на arccosx
3arccos²x + 10arccosx + 3 = 0
arccosx = t
3t² + 10t + 3 = 0
D = 100 - 4*3*3 = 64
t₁ = (- 10 - 8)/6
t₁ = - 3
t₂ = (- 10 + 8)/6
t₂ = - 1/3
1) arccosx = -3
x = cos(-3)
x₁ = cos(3)
2) arccosx = - 1/3
x = cos(-1/3)
x₂ = cos(1/3)
Ответ: x₁ = cos(3); x₂ = cos(1/3)