giải giúp em câu 1 vs ạ, huhu

Giải:

`a)`

ĐKXĐ: `cos(x+pi/4) ne 0<=>x+pi/4 ne pi/2+kpi<=>x ne pi/4+kpi, k in ZZ`

`=>D=RR\\{pi/4+kpi|k in ZZ}`

`b)`

ĐKXĐ: `sin\ (2x)/(x+3) ne 0<=>{(x ne -3),( (2x)/(x+3) ne kpi):}<=>{(x ne -3),(x ne (3kpi)/(2-kpi)):}\quad ( k in ZZ)`

`=>D=RR\\{-3; (3kpi)/(2-kpi)|k in ZZ}`

`c)`

ĐKXĐ: `2sin 2x+1 ne 0`

`<=> sin 2x ne -1/2`

`<=>{(2x ne -pi/6+k2pi),(2x ne (7pi)/6+k2pi):}`

`<=>{(x ne -pi/12+kpi),(x ne (7pi)/12+kpi):}\quad ( k in ZZ)`

`=>D=RR\\{-pi/12+kpi; (7pi)/12+kpi|k in ZZ}`

`d)`

ĐKXĐ: `cos(2x-pi/3) ne 0<=>2x-pi/3 ne pi/2+kpi<=>x ne (5pi)/12+(kpi)/2, k inZZ`

`=>D=RR\\{(5pi)/12+(kpi)/2|k in ZZ}`