Consider the following premises. Joseph is playing squash if and only if it is overcast. It is not overcast. Can we infer the following from them? Joseph is not playing squash or it is sunny.
 From the fact that Joseph is playing squash if and only if it is overcast we can infer that if Joseph plays squash, then it is overcast. From the fact that if Joseph plays squash, then it is overcast, and that it is not overcast we can infer that Joseph is not playing squash. Finally, from the fact that Joseph is not playing squash we can infer that Joseph is not playing squash or it is sunny. Therefore, the answer is yes.