Show that the resultant shear stress is

$=\frac{2T}{a^3{b}^3}[a^2{b}^4+a^2(a^2-b^2)y^2{]}^{\frac{1}{2}}$

for an elliptical shaft $($with semi$-$axes a and b$)$ subjected to a torque, $T$ using a stress function approach.

$(2)$