V=2ab((π/2)+Arcsin(b/√(a^2+b^2))-Arcsin(a/√(a^2+b^2)))
=2ab((π/2)+Arcsin(sin(Arctan(b/a)))-Arcsin(sin(Arcsin(a/b))
=2ab((π/2)+Arctan(b/a)-Arcsin(a/b))
=2ab(2*Arctan(b/a))
=4ab*Arctan(b/a)