青島膠東國(guó)際機(jī)場(chǎng)的顯著特點(diǎn)之一是彎曲曲線的運(yùn)用,衡量曲線彎曲程度的重要指標(biāo)是曲率,曲線的曲率定義如下:若f′(x)是f(x)的導(dǎo)函數(shù),f″(x)是f′(x)的導(dǎo)函數(shù),則曲線y=f(x)在點(diǎn)(x,f(x))處的曲率K=
.
已知函數(shù)f(x)=ae
x-lnx-bcos(x-1)(a≥0,b>0),若a=0,則曲線y=f(x)在點(diǎn)(1,f(1))處的曲率為
.
(1)求b;
(2)若函數(shù)f(x)存在零點(diǎn),求a的取值范圍;
(3)已知1.098<ln3<1.099,e
0.048<1.050,e
-0.045<0.956,證明:1.14<lnπ<1.15.