# NEED help differentation

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#1
will post my question in a min
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#2

i am watching a tutorial on exam solutions . i stuck here in this tutorial he is using a chain rule but why he wrote 7 and 3 . i dont understand this can anyone please explain this to me .
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3 years ago
#3
(Original post by Qer)

i am watching a tutorial on exam solutions . i stuck here in this tutorial he is using a chain rule but why he wrote 7 and 3 . i dont understand this can anyone please explain this to me .
You need to apply the chain rule twice. So for let and

Then
1
3 years ago
#4
(Original post by Qer)

i am watching a tutorial on exam solutions . i stuck here in this tutorial he is using a chain rule but why he wrote 7 and 3 . i dont understand this can anyone please explain this to me .
try and differentiate a trig value with a constant using a substitution it might help
1
3 years ago
#5
(Original post by Qer)

i am watching a tutorial on exam solutions . i stuck here in this tutorial he is using a chain rule but why he wrote 7 and 3 . i dont understand this can anyone please explain this to me .
This is where you have to use the chain rule twice.

Which I think you understand.

Now you have to use the chain rule again as
1
#6
again get confused

so 4tan^5 (3x)
4[tan 3x]^5

20[sec^2 3x] tan 3x]^4

tell whereto used chain rule now
1
#7
0
3 years ago
#8
(Original post by Qer)
again get confused

so 4tan^5 (3x)
4[tan 3x]^5

20[sec^2 3x] tan 3x]^4

tell whereto used chain rule now
Apply chain rule to tan3x
0
#9
(Original post by Desmos)
Apply chain rule to tan3x
so 4tan^5 (3x)
4[tan 3x]^5

20[sec^2 3x] tan 3x]^4

applying chain rule to [tan3x ]^4= 4(sec^2 3x] [tan3x]^3
like that????
0
3 years ago
#10
(Original post by Qer)
so 4tan^5 (3x)
4[tan 3x]^5

20[sec^2 3x] tan 3x]^4

applying chain rule to [tan3x ]^4= 4(sec^2 3x] [tan3x]^3
like that????
No just to . Let and . Then

When you differentiate a composite function, you must differentiate every function which makes it up, whether it's constant, linear, quadratic, trig, exponential etc.
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