函数y=lg(sinx-cosx/sinx+cosx)的定义域 HELP!>oo

分类: 作业答案 • 2021-12-20 09:20:33

问题描述：

答

(sinx-cosx) / (sinx+cosx) > 0
(sin²x-cos²x) / (sinx+cosx)² > 0 => cos 2x => 2kπ + π/2 => 定义域: ( kπ + π/4 , kπ+3π/4)

答

(sinx-cosx)/(sinx+cosx)>0
cosx=0,显然为解,x=kπ+π/2
cosx0,(tgx-1)/(tgx+1)>0---> tgx>1 or tgx kπ+π/4