Relative to the $x$ axis, side BC is oriented at an angle of:

${\theta }_{BC}={180}^{\circ }-53.{13}^{\circ }=126.{87}^{\circ }$

Write a strain transformation equation for side BC:

$$\begin{gathered} -1,000\mu \epsilon ={\epsilon }_x {\cos }^2(126.{87}^{\circ })+{\epsilon }_y {\sin }^2(126.{87}^{\circ }) \\ +{\gamma }_{xy} \sin (126.{87}^{\circ }) \cos (126.{87}^{\circ }) \end{gathered}$$