Question

Cho em hỏi cách giải câu 19 ạ

Answer 1

`2\sqrt{3}sin(x-\pi/8)cos(x-\pi/8)+2cos^2(x-\pi/8)=\sqrt{3}+1`

`<=>\sqrt{3}sin(2x-\pi/4)+cos(2x-\pi/4)=\sqrt{3}`

`<=>\sqrt{3}/2sin(2x-\pi/4)+1/2cos(2x-\pi/4)=\sqrt{3}/2`

`<=>sin(2x-\pi/4+\pi/6)=\sqrt{3}/2`

`<=>sin(2x-\pi/12)=\sqrt{3}/2`

`<=>[(2x-\pi/12=\pi/3+k2\pi),(2x-\pi/12=[2\pi]/3+k2\pi):}`

`<=>[(x=[5\pi]/24+k\pi),(x=[3\pi]/8+k\pi):}`   `(k in ZZ)`

     `->\bb A`