A solid circular rod is made of a material that is assumed to be elastoplestic. Denoting by $TY$ and $y,$ respectively, the torque and the

angle of twist at the onset of yield, determine the angle of twist if the torque is increased to $T=1\mathrm{.}15TY.$

The angle of twist is

$.$ it's answer not $1\mathrm{.}22$ and not $1\mathrm{.}15$