题目

       For more than 40 years, scientists have sought to learn how well human beings can adapt to long periods in space. The International Space Station continues to provide valuable knowledge about spaceflight. But an earlier space station, Skylab, helped make the current space project possible.        Canadian astronaut Chris Hadfield sang aboard the International Space Station on May 12, 2013. His music video has become extremely popular. The astronaut played his own version of David Bowie’s song Space Oddity. He performed while floating weightlessly, with images of pl已知向量（1）求；（2）当时，求的值.