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

The value of cos(sin-1(513)) is equal to:

The solution of the equation 3 tan-1(x) - 2 cot-1(x) = π2 in the first quadrant is ________.

If sin-1(1 - x) - 2sin-1(x) = π2, then find the value of x.