题目

There are many types of reports.A report is simply an account of something that has happened.The commonest are news reports.We get them in newspapers，over radio and on television.Sometimes cinemas also show us newsreels. The main purpose of a newspaper is to provide news.If you examine a newspaper closely，you will find that there are all types of news:accidents，floods，fires，wars，fashions(服装)，sports，books，etc.The news covers everything that happens to people and their surroundings.Sometimes there are news items which are very amusing. A news report is usually very short，一个直角三角形的两直角边的长分别为2cm和cm，则它的面积为    ．