1.由向量a与b垂直,故向量a与向量b数量积=0,故1×（-1）+2n=0,故n＝1/22.由等差数列{an}中有a1+a7+a10=π,故a1+a7+a10=a1+a1+6d+a1+9d=3a1+15d=3(a1+5d)=3a6=π,故a6=π/3,故tan a6＝tan π/3＝√33.sin67.5°/sin22....