1、函数f(x)=3sin(wx+π/4)的最小正周期是2π/|w|=2π/3,得:w=3
所以f(x)=3sin(3x+π/4)
2、f((2/3)a+π/12)=3sin[2a+π/4+π/4]=3sin(2a+π/2)=3cos(2a)=12/5,得:
cos(2a)=4/5
而:cos2a=1-2sin²a=4/5
得:sin²a=1/10
sina=±1/√10=±(√10)/10
1、函数f(x)=3sin(wx+π/4)的最小正周期是2π/|w|=2π/3,得:w=3
所以f(x)=3sin(3x+π/4)
2、f((2/3)a+π/12)=3sin[2a+π/4+π/4]=3sin(2a+π/2)=3cos(2a)=12/5,得:
cos(2a)=4/5
而:cos2a=1-2sin²a=4/5
得:sin²a=1/10
sina=±1/√10=±(√10)/10