1( ) ( ) ( )⇔ − = + −1 2SIN COS 3 1 2SIN 1 SINPT X X X X( 2 )⇔ − = + −...

1. ĐK: 1

( ) ( ) ( )

⇔ − = + −1 2sin cos 3 1 2sin 1 sinPt x x x x

(

²

)

cos 2sin cos 3 1 sin 2sinx x x x x⇔ − = +cos 3 sin sin2 3 cos2x x x x   ⇔ x− x= x+ x⇔ π +xữ=  x−π ữ 1 3 1 3cos sin sin2 cos 2 cos cos 22 2 2 2 3 6⇔ + =π x x− +π k πhayπ + = − + +x x π k π2 2 2 23 6 3 6= − +⇔ = −x π k π (loaùi) 22 2x π k π , k ∈ Z (nhaọn)18 3− ≥ ⇔ ≤6 5 0