An orthotropic lamina has thermal expansion coefficients (alpha_{1}=-4.0) (left(10^{-6} ight) mathrm{m} / mathrm{m} / mathrm{K}) and (alpha_{2}=79left(10^{-6}

An orthotropic lamina has thermal expansion coefficients \(\alpha_{1}=-4.0\) \(\left(10^{-6}\right) \mathrm{m} / \mathrm{m} / \mathrm{K}\) and \(\alpha_{2}=79\left(10^{-6}\right) \mathrm{m} / \mathrm{m} / \mathrm{K}\). Determine

(a) the angle \(\theta\) for which the thermal expansion coefficient \(\alpha_{y}=0\), and

(b) the angle \(\theta\) for which the thermal expansion coefficient \(\alpha_{x y}\) has its maximum value.