A:﹣3﹣4i
B:﹣3+4i
C:3﹣4i
D:3+4i
观察和实验是学习科学的重要方式,下列实验中观察到的颜色正确的是( )
These aren't ________ cards. They're_______
已知函数f(x)的导函数为f′(x),若fx=f'π9sin3x+cos3x,则f'π9=____