00:01
Okay, so we want to differentiate y equals sine of x to the 9, and we want to differentiate y equals sign of x or to the power of 9.
00:09
So for both of these, we need to use the chain rule.
00:11
So let's firstly look at y equals sign of x to the power 9.
00:17
So to use the chain rule, we need to make some sort of substitution.
00:20
So here we have x to the power 9 as this sort of inner function, and we have a sign as the aata function.
00:27
So i'm going to write u equals x to the 9.
00:29
And then by the chain rule so then y is equal to sign of u so if u is equal to x to the nine then y is sign of x to the nine which is sign of u so then by the chain rule d y by d x is d y by d u times d u by d x so this is the chain rule and then we can take both of these derivatives since y is equal to sign of u y by d u is just cause of u so cause of u and d u by d x well u is equal to x to the nine so differentiating x to the nine we get nine x to the eight so now we can plug in u here to get back everything in terms of x we know u is equal to x to the nine so we have cos of x to the nine times nine x to the eight and it doesn't look right like this, so i'm just going to change it around slightly, but it's the same answer.
01:35
9x to the 8 times the cause of x to the 9.
01:39
So this is part a for part b...