**Here are some examples of using the word «ascertain»:**
1. The police are trying to ascertain the identity of the suspect.
2. We need to ascertain the cause of the accident before we can make any conclusions.
3. Scientists are working to ascertain whether climate change is causing more extreme weather events.
4. The teacher asked the students to ascertain the meaning of an unfamiliar word in the text.
5. It is difficult to ascertain the exact number of people attending the event, as there was no registration.
6. The insurance company is investigating the claim to ascertain if it is valid.
7. The company conducted a survey to ascertain customer satisfaction with its products and services.
8. The doctor asked the patient to undergo tests to ascertain the nature of the illness.
9. The committee is trying to ascertain public opinion on a proposed new law.
10. The detective used various methods to ascertain the truthfulness of the witness's testimony.