文档介绍：对数函数(2) Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 2017-3-29 京翰教育中心、对数函数 y = log a x ( a >0 且 a ≠ 1 ) 是指数函数 y = a x ( a >0 且 a ≠ 1 ) 的反函数。 Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 2017-3-29 京翰教育中心 2、对数函数的图象与性质: 函数底数图象定义域值域定点值分布单调性趋势 y = log a x ( a >0 且 a≠1 ) a > 1 ( 0 , + ∞)R ( 1 , 0 ) 即 x = 1 时, y = 0 当 x>1 时, y>0当 0<x <1 时, y<0在 ( 0 , + ∞ ) 上是增函数底数越大,图象越靠近 x 轴 0 < a < 1 当 x>1 时, y<0当 0<x<1 时, y>0在( 0 , + ∞)上是减函数底数越小,图象越靠近 x 轴 1x yo 1x yo ??????????????中另一个在中一个在或),1( ),1,0(,0 10 ),1(,)1,0(,0 logNa N NaNaN a Evaluation only. Evaluation only. Created with Client Profile . Created with Client Profile . Copyright 2004-2011 Aspose Pty Ltd. Copyright 2004-2011 Aspose Pty Ltd. 2017-3-29 京翰教育中心 4 3 2 1 -1 -2 -3 2 4 6 8 10 y=log 2x 4 3 2 1 -1 -2 -3 2 4 6 8 10 y=log 2x 、比较下列各组数中两个数的大小: (1) log 2 3 . 4 与 log 2 8 . 5 解: ∵ y = log 2 x在 ( 0 , + ∞) 上是增函数且 3 . 4 <8 . 5 ∴ log 2 3 . 4 < log 2 8 . 5 Evaluation o