What is the derivative of this function y=csc^-1(4x^2)y=csc1(4x2)?

1 Answer
Dec 27, 2017

dy/dx=-4/(xsqrt(16x^4-1)dydx=4x16x41

Explanation:

We first need to work the derivative of csc^-1(x)csc1(x)
We can start with this:

y = csc^-1(x) -> csc(y)=xy=csc1(x)csc(y)=x

Now differentiate both sides implicitly with respect to xx to get:

-dy/dxcsc(y)cot(y)=1dydxcsc(y)cot(y)=1

-> dy/dx = -1/(csc(y)cot(y))dydx=1csc(y)cot(y)

Now, using:

sin^2(y)+cos^2(y)=1sin2(y)+cos2(y)=1

Divide this identity through by sin^2(y)sin2(y) to get:

1+cot^2(y)=csc^2(y) -> cot(y) = sqrt(csc^2(y)-1)1+cot2(y)=csc2(y)cot(y)=csc2(y)1

We can now plug this into our equation for dy/dxdydx to get:

dy/dx = -1/(csc(y)sqrt(csc^2(y)-1)dydx=1csc(y)csc2(y)1

Using csc(y)=xcsc(y)=x we may now rewrite dy/dxdydx in terms of xx:

dy/dx = -1/(xsqrt(x^2-1)dydx=1xx21

So now that we have the derivative of csc^(-1)xcsc1x we can now apply the chain rule to obtain the derivative of y=csc^-1(4x^2) y=csc1(4x2)

-> dy/dx= -1/((4x^2)sqrt((4x^2)^2-1)).d/dx(4x^2)dydx=1(4x2)(4x2)21.ddx(4x2)

=-(8x)/((4x^2)sqrt((4x^2)^2-1))=8x(4x2)(4x2)21

Now simplify:

=-4/(xsqrt(16x^4-1)=4x16x41