00:01
In this question, we are talking about the chain rule.
00:06
The question specifically asks whether or not we get the same derivative for a composite function if we write it as a composite in different ways.
00:21
For example, we can write this function y, that is cos of 6x plus 2, as cos of u where u is 6x plus 2, or codes of 2 where u is 6x plus 2, or codes of 2 where you, where u is 3x plus 1.
00:37
So the chain rule shows us that the derivative is the same no matter how we write it.
00:43
And so we're just going to see that in, we're going to demonstrate that in this question.
00:53
First of all, we're going to find the derivative of y with respect to x for part a, where y is close of u and u is 6x plus 2.
01:05
The chain rule tells us that dydx is equal to dydu times du d 'dx.
01:25
D .y .d .u is the derivative of this function, which is negative sign of u.
01:35
And then the derivative of u with respect to x is 6.
01:47
Now, part b.
01:54
Again, we have the derivative of y with respect to x is equal to the derivative of y with respect to u, times the derivative of u with respect to x.
02:09
Only this time, the derivative of y with respect to u requires the use of chain rule again...