1-2sinxcosx/cos2x-sin2x=1-tanx/1+tanx

来源:学生作业帮助网 编辑:作业帮 时间:2024/10/01 10:42:13
1-2sinxcosx/cos2x-sin2x=1-tanx/1+tanx
x)35*̫H/F@QnIb^6I*'R~ )>ݾž@y5eCs m(a0B&[$XB"V^ AP,dGד/g.y{)H *8E [۟u6U|D4moJ@|9qE3b}~qAb4l$

1-2sinxcosx/cos2x-sin2x=1-tanx/1+tanx
1-2sinxcosx/cos2x-sin2x=1-tanx/1+tanx

1-2sinxcosx/cos2x-sin2x=1-tanx/1+tanx
左边=(sin²x+cos²x-2sinxcosx)/(cos²x-sin²x)
=(cosx-sinx)²/(cosx+sinx)(cosx-sinx)
=(cosx-sinx)/(cosx+sinx)
上下除以cosx
且 sinx/cosx=tanx
所以左边=(1-tanx)/(1+tanx)=右边
命题得证

b(n+1)/bn
=-2a(n+1)÷(-2an)
=a(n+1)/an
=q
选A
(-2)△5即A=-2,B=5
所以(-2)△5=-2×5+5-(-2)
=-10+5+2
=-3