sin(-15π/8)大于sin(-14π/9)
tan89°大于tan91°过程sin(-15π/8)=sin(-2π+π/8)=sin(π/8)sin(-14π/9)=sin(-2π+4π/9)=sin(4π/9)因为sin在0到π2上是增函数所以sin(-15π/8)小于sin(-14π/9) 额，抱歉刚才的答案有点错tan89°大于0，tan91°小于0所以tan89°大于tan91°