Question

If cos −1 α+cos −1 β+cos−1
γ=3π then proof (α^3+beta^3+gamma^3) - (1/alpha + 1/beta +1/gamma) =0​

Answer 1

If cos-1 α + cos -1 β + cos-1 γ = 3π, then α(β + γ) + β(γ + α) + γ(α + β) equals .