题目

阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。 A lecturer was giving a lecture to his students on stress (压力) management. He raised a glass of water and asked them, “How heavy do you think this glass of water is?” The students' answers ranged from 20g to 500g. It doesn't matter on the absolute (weigh). It depends on how long you hold . If I hold it for a minute, it is OK. If I hold it for an hour, I'll have ache in my right arm. If I hold it for a day, you will have to call an ambulance. It's exactly the same weight, but the（1）若sinα=513且a是第二象限角，求cosa 及tana值；（2）若sinα-cosa=34，求sin2a的值．