Câu 42: Một vật dao động điều hòa x co t = + 12 s(2 )  
(cm). chọn gốc thời gian lúc vật qua vị trí có li độ +6 cm theo chiều dương.
Giá trị của

là:A
3
rad 
 = − B.
2
3
 =  rad C.
2
3
 = −  rad
D.
3
 =  rad

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