7-7-33 derivative of inverse csch x
X
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Find the derivative of Y with respect to Theta.
So if we let F of X equal hyperbolic cosecant X, then F
inverse of X is hyperbolic cosecant inverse of X.
So the derivative of that is going to be -1 divided by the
derivative of that hyperbolic cosecant is hyperbolic cosecant
of the F inverse of X times hyperbolic cotangent of the F
inverse of X.
That was negative because it starts with AC.
It's a Co function, so the hyperbolic cosecant of the
hyperbolic cosecant of inverse of X is just X.
We know that the hyperbolic cotangent based off of our
identity of the hyperbolic cosine squared X minus the
hyperbolic sine squared X equal 1.
If we divided them all by hyperbolic sine squared, we'd
get hyperbolic cotangent X -, 1 equal hyperbolic cosecant
squared X.
So we're going to replace this hyperbolic cotangent with the
square root of hyperbolic cosecant squared X + 1.
And remember that X is really this whole hyperbolic cosecant
inverse of X.
So now these are going to cancel, leaving us an X ^2 + 1.
So our formula for the derivative of just plain old
hyperbolic cosecant inverse of X is -1 / X sqrt X ^2 + 1.
Now we're going to have to do the chain rule for the actual
problem.
So we're going to have -1 over this 1/8 to the Theta square
root, 1/8 to the two Theta plus one times DD Theta of 1/8 to the
Theta.
Well, the derivative of 1/8 to the Theta is the negative
natural log of 1/8 tie.
Actually the negative came from there times 1/8 to the Theta.
So now if we simplify this up, we can think of 1/8 as 8th to
the -1 and the negative and the negative there can cancel.
If I get a common denominator in the bottom, we'd get one to the
two Theta, which is 1 plus 8 to the two Theta, all over 8 to the
two Theta, and the 1 / 8 to the thetas top and bottom are going
to cancel.
So now we have the square root of this 8 to the two Theta, the
square root and the two are going to cancel.
So that's going to leave us 8 Theta, 8 to the Theta outside.
And because it was in the denominator, we're going to move
it up to the numerator.
So 2 lane 3 * 8 to the Theta over the square root, 1 + 8 to
the two Theta.
Or if we had wanted to, we could actually think of that as lane
of eight.
Oh wait, I did this one backwards right here.
8 is 2 ^3, so that would have been 3-2.
Or we could have thought of it as lane 8 * 8 to the Theta all
over the square root 1 + 8 to the two Theta.