1. GIẢI CÁC PHƯƠNG TRÌNH SAU

Bài 3.1. Giải các phương trình sau: a) ^{2 cos 3}

(

^x−60

⁰

)

^{+ =1 0 b) 2sin 2}_ ^x−π₆^_^{+ 3 0=}x d) ^ ₋π ^_{+ =}3 cot 3 03 tan 20

0

1 0+ + =c)   4x 3 HD Giải a) ^{2 cos 3}

(

^x−60

⁰

)

^{+ = ⇔1 0 cos 3}

(

^x−60

⁰

)

^{= − ⇔1}₂ ^{cos 3}

(

^x−60

⁰

)

^=cos120

⁰

 − = +  = +

0

0

0

0

0

3 60 120 360 90 120x k x k⇔ ⇔ ∈3 60 120 360 20 120 , k− = − + = +  ℤ2sin 2 3 0 sin 2 3 sin 2 sinb) ^ ₋π ^_{+ = ⇔} ^ ₋π ^_{= − ⇔} ^ ₋π ^₌ ^₋π ^x x x       6 6 2 6 3       π π π π π − = − + = − +2 2 6 3 12 ,ℤπ π π π π π2 2 3 − = + +  = + 6 3 4x x ^⇔tan_4^x+20

⁰

^_^{=tan 30}

( )

⁻

⁰

0

0

1+ + = ⇔ + = −3 tan 20 1 0 tan 20c)       4 4 3   x k x k k ⇔ +20

⁰

= −30

⁰

+ 180

⁰

⇔ = −200

⁰

+ 720 ,

⁰

∈^ℤ3 cot 3 0 cot 3 cot cotd) ^ ₋π ^_{+ = ⇔} ^ ₋π ^_{= − ⇔} ^ ₋π ^₌ ^₋π ^3 3 3 6 ⇔ − = − +π π π ⇔ = +π π, ∈ℤ3 6 6