The cross section of a thin tube having variable wall thickness t is shown in figure 1a. The median line of the cross section is a circle of radius 7, and the thickness is given by the following equation: tto 1+ sin Ө where to is the thickness at the section where 8 = 0. If the tube is subject to a torque T, what is the maximum shear stress tmax? What is the minimum shear stress tmin? What is the angle of twist per unit length? A 8 x 20 Figure la