来自陈希军的问题
【设0<x1<x2<π2.(Ⅰ)证明:x1>sinx1(Ⅱ)x1sinx2cosx1>x2sinx1cosx2.】
设0<x1<x2<π2.
(Ⅰ)证明:x1>sinx1
(Ⅱ)x1sinx2cosx1>x2sinx1cosx2.
1回答
2020-11-28 23:55
【设0<x1<x2<π2.(Ⅰ)证明:x1>sinx1(Ⅱ)x1sinx2cosx1>x2sinx1cosx2.】
设0<x1<x2<π2.
(Ⅰ)证明:x1>sinx1
(Ⅱ)x1sinx2cosx1>x2sinx1cosx2.
证明:(Ⅰ)令f(x)=x-sinx(0<x<π2),∴f′(x)=1-cosx≥0,∴f(x)=x-sinx(0<x<π2)为增函数,∵0<x1<π2,∴f(x1)>f(0),即x1-sinx1>0,∴x1>sinx1;(Ⅱ)令g(x)=xcotx(0<x<π2)...