a=sin5π/7,b=cos5π/7,c=tan5π/7

问题描述:

a=sin5π/7,b=cos5π/7,c=tan5π/7
abc那个最大,那个最小?

a=sin5π/7=sin2π/7>0
b=cos5π/7=-cos2π/7>-1
c=tan5π/7=-tan2π/7cos5π/7>tan5π/7