00:02
Alright, in this problem, i'm going to take the derivative of this using the quotient rule.
00:07
Then i'm going to switch it to signs and cosines and take the derivative again, and then i'm going to show you that the two derivatives are the same.
00:19
Okay, this is a quotient, so i have to use the question rule.
00:22
It's the bottom times the derivative of the top, and the derivative of the tangent of x is secan squared of x, minus the derivative of 1, which is 0.
00:34
So bottom, derivative of the top, minus the top, times the derivative of the bottom and the derivative of secan of x is secan x tangent x and then the whole thing over the bottom squared so i'm going to go ahead and multiply the top out so i have secant to the third x there i'm going to distribute i get minus sikin x tangent squared x minus minus which makes plus secan x tangent x all over sikin squared x.
01:23
Now i notice that every piece on the top has a sikin in it, so i'm going to factor out the sikin of x.
01:31
So i get sikin squared x minus tangent squared x plus tangent x, all over sikin squared x.
01:48
All right, we know the identity 1 plus tangent squared x equals siken squared x.
01:56
So then sqn squared minus tangent squared equals to 1.
02:11
So one of these sequins will cancel with one of these, or this sequence will cancel with one of those.
02:18
So now we have one plus tangent x over sicken x.
02:26
Okay, so that's the derivative, the first way.
02:35
Now i'm going to take the problem, f of x equals tangent x minus one over sicken x.
02:45
I'm going to change everything to sine and cosine.
02:47
So i get sine x over cosine x minus 1 over 1 over the cosine of x.
02:58
So here i have a complex fraction or a four -story fraction.
03:02
And so what i'm going to do is simplify it by getting a common denominator for all the fractions and multiplying...