Question

求下列导数 多谢 ~~~~

Answer 1

一、
用到的导数知识：函数积的求导法则
f'(x)=(sinx/x^2)'
=[
(sinx)'x^2
-
sinx(x^2)'
]
/
(x^2)^2
=[
(x^2)cosx
-
(2x)sinx
]
/
x^4
=cosx/x^2
-
2sinx/x^3
二、
用到的导数知识：函数的和、积的求导法则
f'(x)=(
3x^4
-
4x^2
sinx
+
2
/
x
)'
=(
3x^4
)'
-
(
4x^2
sinx
)'
+
(
2
/
x
)'
=12x^3
-
4[
(x^2)'sinx
+
x^2(sinx)'
]
-
2x^(-2)
=12x^3
-
4[
2xsinx
+
x^2(cosx)
]
-
2x^(-2)
=12x^3
-
8xsinx
-
4x^2(cosx)
-
2x^(-2)