这个题目有没有简单易懂的方法!

1个回答

  • S1=sin(π/7)>0,

    S2=sin(π/7)+sin(2π/7)>0

    S3=sin(π/7)+sin(2π/7)+sin(3π/7)>0,

    S4=sin(π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)>0,

    S5=sin(π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)+sin(5π/7)>0

    S6=sin(π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)+sin(5π/7)+sin(6π/7)>0

    S7=sin(π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)+sin(5π/7)+sin(6π/7)+sin(π)>0,

    S8=sin(1π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)+sin(5π/7)+sin(6π/7)+sin(π)+sin(8π/7)

    =sin(1π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)+sin(5π/7)>0

    S9=sin(1π/7)+sin(2π/7)+sin(3π/7)+sin(4π/7)>0

    S10=sin(1π/7)+sin(2π/7)+sin(3π/7)>0

    S11=sin(1π/7)+sin(2π/7)>0

    S12=sin(1π/7)>0

    S13=0

    S14=0+sin(2π)=0

    ……

    在S1,S2,…,S100中,为0的项共有14项,其余项都为正数.

    故在S1,S2,…,S100中,正数的个数是86.