## College Physics (7th Edition)

a). $\theta_{r2}=alpha-\theta_{i1}$ b). $\theta_{r2}=55^{\circ}$
a). $\theta_{r2}=[90^{\circ}-(90^{\circ}+\theta_{r1}-alpha)]$ or, $\theta_{r2}=alpha-\theta_{r1}$ , $[\theta_{i2}=\theta_{r2}, \theta_{i1}=\theta_{r1}]$ So, $\theta_{r2}=alpha-\theta_{i1}$ b). from part a, $\theta_{r2}=alpha-\theta_{i1}=115^{\circ}-60^{\circ}=55^{\circ}$