Consider the two-rod linkage in Figure 4.24. A configuration $\left(\theta_A, \theta_B\right)$ of this linkage is a singular configuration if at configuration $\left(\theta_A, \theta_B\right)$ the operational space path obtained by holding $\theta_A$ fixed and varying $\theta_B$ is tangent to the path obtained by holding $\theta_B$ fixed and varying $\theta_A$. Determine the singular configurations of this linkage.