1. ĐK: 1
( ) ( ) ( )
⇔ − = + −
1 2sin cos 3 1 2sin 1 sin
Pt x x x x
(
2 )
cos 2sin cos 3 1 sin 2sin
x x x x x
⇔ − = +
cos 3 sin sin2 3 cos2
x x x x
⇔ x − x = x + x ⇔ π + x ÷ = x − π ÷
1 3 1 3
cos sin sin2 cos 2 cos cos 2
2 2 2 2 3 6
⇔ + = π x x − + π k π hay π + = − + + x x π k π
2 2 2 2
3 6 3 6
= − +
⇔ = − x π k π (loại) 2
x π k π , k ∈ Z (nhận)
2 2
18 3
− ≥ ⇔ ≤
6 5 0
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