-√2/2=sin(-π/4)=sin(5π/4)
=sin(2kπ-π/4)=sin(2kπ+5π/4)
因为sinx在(2kπ-π/4,2kπ+π/2)是增函数
所以由sin(2x-π/4)>sin(2kπ-π/4)
则2x-π/4>2kπ-π/4
而sinx在(2kπ+π/2,2kπ+5π/4)是减函数
所以由sin(2x-π/4)>sin(2kπ+5π/4)
则2x-π/4
【急】问一道高一三角函数题如图我对灰色背景的那一部分不太清楚 为什么能得出这个结论?
-√2/2=sin(-π/4)=sin(5π/4)
=sin(2kπ-π/4)=sin(2kπ+5π/4)
因为sinx在(2kπ-π/4,2kπ+π/2)是增函数
所以由sin(2x-π/4)>sin(2kπ-π/4)
则2x-π/4>2kπ-π/4
而sinx在(2kπ+π/2,2kπ+5π/4)是减函数
所以由sin(2x-π/4)>sin(2kπ+5π/4)
则2x-π/4