题目

Shopping in the United States changes a lot．About ninety years ago most people shopped in small stores that were owned by one person or a family．Women went from the bakery to the butcher’s to the grocer and on to the fruit and vegetable seller in order to get their food for the week．Then, about sixty years ago, supermarkets were born．In a supermarket, people could get all the different kinds of food they needed without going to different stores．        The next big change in shopping in the United States was the shopping mall．A shopping mall is a group of stores under one r（1）已知，求tanα的值．（2）已知α为锐角，且tanα=4，求的值．