If sec θ-cos θ, y= secⁿ θ- cosⁿ θ then (dy/dx)²=

d/dx{Tan^-1 1/√x²-1}=

If x= a(θ+sin θ), y=a(1-cosθ) then d²y/dx² at θ=π/4 is

d/dx{Tan^-1x/√1-x²+Sec^-11/√1-x²}=

d/dx{Tan^-1√(x²/a²-x²)}=