求复合导数.y=lnsin(1/x)y=lncot(x/2)要过程
1个回答

答案分别为-(1/x²)cot(1/x)和-cscx

解法:

我用导数符号dy/dx了,因为用这个的链式法则求复合函数的导数时很好用的

y=lnsin(1/x)

dy/dx=dlnsin(1/x)/dsin(1/x)·dsin(1/x)/d(1/x)·d(1/x)/dx

=1/sin(1/x)·cos(1/x)·(-1/x²)

=-(1/x²)cot(1/x)

y=lncot(x/2)

dy/dx=dlncot(x/2)/dcot(x/2)·dcot(x/2)/d(x/2)·d(x/2)/dx

=1/cot(x/2)·[-csc²(x/2)]·(1/2)

=-(1/2)sin(x/2)/cos(x/2)·1/sin²(x/2)

=-(1/2)·1/[sin(x/2)cos(x/2)]

=-1/sinx

=-cscx