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问题: 求下列函数的导数

求下列函数的导数:y=xcos(2x+pai/2)sin(2x+pai/2)

解答:

y=xcos(2x+pai/2)sin(2x+pai/2)
=(1/2)xsin(4x+π)
=-(1/2)xsin4x
所以y′=-(1/2)[(x)′sin4x+x(sin4x)′]
=-(1/2)(sin4x+4xcos4x)
=-(1/2)sin4x-2xcos4x