题目

    Everywhere I look outside my home I see people busy on their high-tech devices, while driving, walking, shopping, even sitting in toilets. When connected electronically, they are away from physical reality.  People have been influenced to become technology addicted. One survey reported that “addicted” was the word most commonly used by people to describe their relationship to iPad and similar devices. One study found that people had a harder time resisting the allure of social media than they did for sleep, cigarettes and alcohol.  The main goal of technology companies已知向量=（cosx，sinx），=（-cosx，cosx），=（-1，0）．（Ⅰ）若，求向量、的夹角；（Ⅱ）当时，求函数的最大值．