题目

，，，则tanα=（ ） A． B．    C．    D． 答案：D【考点】同角三角函数间的基本关系． 【专题】计算题；三角函数的求值． 【分析】把sinα与cosα代入sin2α+cos2α=1中，求出m的值，确定出sinα与cosα的值，即可求出tanα的值． 【解答】解：∵sinα=，cosα=， ∴sin2α+cos2α=1，即+=1， 解得：m=0或m=8， 当m=0时，sinα=﹣，cosα=，此时tanα=﹣； 当m=8时，sinα=，cosEnergy pod:It was designed by a US company with NASA technology. It puts the human body in the best sleeping position and blocks outside noise to create an ideal napping experience. Silicon Valley high-tech companies such as Google provide the Pod for employees.White noise radio:White noise is a sound signal that contains equal power and frequency. Some radios provide white noise to mask other noises so that people can sleep without disturbance.High-tech sleepwear:A US-based company designs a nightgown with special fabric that stimulates blood flow to tired muscles helping one relax in deeper restorative sleep.Emu pillow:Inspired by emu that buried its head in sands when it’s scared, a type of pillow has been designed in China for office workers to take a nap, safe and sound. It turns the computer desk into a sleep hub with even two pockets to store the hands.小题1:These are designed for those who   .A．have enough sleep.B．are working for high-tech companies.C．are in poor health.D．are victims of sleeping sickness.小题2:Which of the following is produced with the help of a kind of bird?A．White noise radio.B．Emu pillow. C．High-tech sleepwear.D．Energy Pod.小题3:How do you probably get the information?A．From a book.B．From a radio program.C．From a newspaper.D．From a text message.