Question

y= cos 9x

Answer 1

and?

Answer 2

Find the derivative of the following function

Answer 3

Do you know the chain rule? :)

Answer 4

Yeah but I kinda forgot it

Answer 5

The chain rule is \(\dfrac{dy}{dx}=\dfrac{dy}{du}\cdot\dfrac{du}{dx}\) :)

Answer 6

Let \(u\) be \(9x\) :)

Answer 7

Alright then tho i didnt get it that much xD

Answer 8

There is 9 more btw

Answer 9

For example,\[\frac d{dx}\sin(5x)\]\[=\frac d{d(5x)}\sin(5x)\cdot\frac d{dx}5x\]\[=\cos(5x)\cdot5\]\[=5\cos(5x)\]

Answer 10

Get it? :)

Answer 11

Hold on ?

Answer 12

What about an answer to my question?

Answer 13

Can you try to do it by yourself first? :)

Answer 14

Aight

Answer 15

ddxcos(9x)
=dd(9x)cos(9x)⋅ddx9x
=sin(9x)⋅9
=9sin(9x)

Answer 16

well done, except the negative sign emerged from differentiating cosine :D

Answer 17

What do you mean ?

Answer 18

-9sin(9x)

Answer 19

Oh i see , but why ?

Answer 20

because \(\dfrac d{d\theta}\cos\theta=-\sin\theta\) :)

Answer 21

Oh i see thank you

Answer 22

What about the others ? I mean like the other questions.

Answer 23

ShalI post it too

Answer 24

Just let \(u\) be whatever you feel appropriate :)

Answer 25

For example in \(y=(x+1)^4\), let \(u=x+1\)
In \(y=\sin(\sqrt x)\), let \(u=\sqrt x\) :)

Answer 26

How bout this , y=(cos 5x) (sin5x)

Answer 27

You can use the product rule for this :)