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1、1+cosx/1-cosx + 1-cosx/1+cosx=4cot^2x+2

来源:学生作业帮 编辑:作业帮 分类:数学作业 时间:2024/05/15 06:34:37
1、1+cosx/1-cosx + 1-cosx/1+cosx=4cot^2x+2
2、sinx+tanx/cotx+cscx=sinx*tanx
恩有括号的那个
(1+cos x)/(1-cos x)+(1-cos x)/(1+cos x)通分
=((1+cos x)^2+(1-cos x)^2)/1-cos^2(x)
=2*(1+cos^2(x))/sin^2(x)
因为1= cos^2(x)+sin^2(x)
2*(1+cos^2(x))/sin^2(x)
=2*(sin^2(x)+2*cos^2(x))/sin^2(x)
=4cot^2(x)+2
sinx+tanx = (sinx*cosx+sinx)/cosx = sinx/cosx *(1+cosx)
cotx+cscx = cosx/sinx + 1/sinx = (1+cosx)/sinx
(sinx+tanx)/(cotx+cscx)=sinx*sinx/cosx
=sinx*tanx