Find the value of the expression tan[12 cos−1(2√5)]. [Hint: tan(θ2) = √(1 − cos θ1 + cos θ)]

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.