In triangle , , and angle is obtuse. What does the Triangle Inequality tell you about possible lengths for ? What do you know about the length of from the size of its opposite angle? Combine what you know about the length of into an inequality of the form  .

A city bus runs between the library, grocery store, and post office. The bus begins at the library and drives 5 kilometers along a straight road to the grocery store. The next stop is the post office is 12 kilometers from the grocery down another straight road. Can the library be 14 kilometers from the post office? Explain your reasoning.