1 99:59:59,999 --> 99:59:59,999 So now we're going to take the derivative of the sine of 2 99:59:59,999 --> 99:59:59,999 the natural log of x squared, so now we have a function 3 99:59:59,999 --> 99:59:59,999 thats the composite of a function thats a composite of another function 4 99:59:59,999 --> 99:59:59,999 So one way you could think of it: if you set f(x) 5 99:59:59,999 --> 99:59:59,999 equal to sine of x and g of x 6 99:59:59,999 --> 99:59:59,999 g of x being the natural log of x 7 99:59:59,999 --> 99:59:59,999 the natural log of x, and lets say 8 99:59:59,999 --> 99:59:59,999 h of x equaling x squared 9 99:59:59,999 --> 99:59:59,999 then this thing right here is the exact same thing as 10 99:59:59,999 --> 99:59:59,999 take the derivative with respect to x 11 99:59:59,999 --> 99:59:59,999 f of g of h of x 12 99:59:59,999 --> 99:59:59,999 and what I want to do is kind of think of how I want to do it in my head 13 99:59:59,999 --> 99:59:59,999 not having to write all of the chain rule notation, so the way I would think 14 99:59:59,999 --> 99:59:59,999 about this if I were doing this in my head is the derivative of this outer function of f with respect to the level of composition directly below it 15 99:59:59,999 --> 99:59:59,999 so the derivative of sine of x is consine of x 16 99:59:59,999 --> 99:59:59,999 but instead of it being cosine of x it's going to be cosine of whatever was inside of here, so it's going to be cosine of 17 99:59:59,999 --> 99:59:59,999 natural log, cosine of natural log of x sqaured 18 99:59:59,999 --> 99:59:59,999 and so you could really view this, this part that I just 19 99:59:59,999 --> 99:59:59,999 wrote right over here as f prime of g of h of x 20 99:59:59,999 --> 99:59:59,999 if you want to keep track of things 21 99:59:59,999 --> 99:59:59,999 Just took the derivative of the outer with respect to whatever was inside of it 22 99:59:59,999 --> 99:59:59,999 have to take the derivative of the inside with respect to x, but now we have 23 99:59:59,999 --> 99:59:59,999 another composite function, so we're going to multiply this times-we're going to do the chain rule 24 99:59:59,999 --> 99:59:59,999 again, the derivative of, we're going to take the derivative of 25 99:59:59,999 --> 99:59:59,999 ln with respect to x squared 26 99:59:59,999 --> 99:59:59,999 so the derivative of ln x is 1 over x, but now we have