Cho hàm số y = f ( x ) = cos 2 x 1 + sin 2 x . Biểu thức f ' π 4  bằng

A.-3

B. 8 3 ⋅

C. −    8 9

D. − 8 3 ⋅

cái này bn vào trang toán hỏi nhé

a, I have played soccer for 5 years

b, My school is different from your school

c, His hobby is playing computer games

d, Her book is different from mine

e, Coffee is grown in Brazil

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