已知数列an是等差数列,且a1+a2+a3= 2π,则tan(a3+a5)=?怎么能求出公差?_数学解答

已知数列an是等差数列,且a1+a2+a3= 2π,则tan(a3+a5)=?
怎么能求出公差?

人气：499 ℃　时间：2019-11-02 18:03:16

解答

a1 a1 d a1 2d=2π,
3a1 3d=2π,
a1 d=2π/3.==>a2=2π/3.
a1 a1 d a1 2d=a1 d 2a2=3a2=2π.
a3 a5=a1 2d a1 4d
=2a1 6d.
=2(a1 3d)=2a4.
…差了条件,a1=?