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问题: 导数

1.求下列函数的导数

(1).f(x)=(sinax)^2*cosbx

(2).y=x^2√(x+√x)

2.f(x)=1/3x*x*x+3xf`(0),则f`(1)=?

解答:

1.求下列函数的导数

(1).f(x)=(sinax)^2*cosbx

(2).y=x^2√(x+√x)

2.f(x)=1/3x*x*x+3xf`(0),则f`(1)=?


1,
1)f(x)=(sinax)^2*cosbx
f'(x) = 2(sinax)*(acosax)cosbx + (sinax)^2(-bsinbx)
= 2acosax*sinax*cosbx -b(sinax)^2*sinbx

2) y=x^2√(x+√x)
y' = 2x*sqrt(x+sqrt(x))+ x^2*(x+sqrt(x))^(-1/2)*(1+x^(-1/2))
=2x*(x+x^(1/2))^(1/2)+x^2*((x^(1/2)+1)/x^(1/2))/(x+x^(1/2))^(1/2)


2. f(x)=1/3x*x*x+3xf`(0)
f'(x) = x^2 + 3f'(0),
f'(0) = 3f'(0), f'(0) = 0;
f'(x) = x^2,

f'(1) = 1.