题目

       A company has designed a water bottle,the Memobottle,which is ideal for the office worker’s bag,because it’s completely flat.With the same shape as a piece of paper,the Memobottle is a reusable water bottle that slides into your bag to lie next to books and laptops.The bottle,which can also be washed in a dishwasher,is designed to help reduce the number of plastic bottles in landfills（填埋）.        Two creative people Jesse Leeworthy and Jonathan Byrt,both 28,designed the bottle to be convenient to carry and environmentally friendly.It is made from a durab已知α，β∈(0，π2)，且tanα，tanβ是方程x2-5x+6=0的两根．（1）求α+β的值；  （2）求cos（α-β）的值．