Find the derivative of 8^{3^{x^2}} ?

I got the first step but I'm not sure what to do next

ln(8)*8^{3^{x^2}}*\frac{d}{dx}(3x^2)

1 Answer
Jun 15, 2018

(dy)/(dx)=ln3*ln8*2x(3^(x^2)*8^(3^(x^2)))

Explanation:

We know that,

color(red)((P)lnx^n=n*lnxto[ Power /coefficient rule ]

color(blue)((S)ln(X*Y)=lnX+lnY)to[ product/sum rule ]

Let,

y=8^(3^(x^2))...to(1)

For simplicity we take, N=3^(x^2)

:.y=8^N

Taking natural log ,we get

lny=ln8^N=Nln8 ...tocolor(red)(Apply(P) ,

where , N=3^(x^2)

=>lny=3^(x^2)*ln8...to(2)

Again taking natural log ,

ln(lny)=ln(3^(x^2)*ln8)...tocolor(blue)(Apply(S)

=>ln(lny)=ln(3^(x^2))+ln(ln8)

=>ln(lny)=x^2*ln3+ln(ln8)

Diff.w.r.t. x ,we get

1/lny*1/y(dy)/(dx)=2x*ln3+0

=>1/(ylny)*(dy)/(dx)=2xln3

=>(dy)/(dx)=ylny(2xln3)

From (1) and (2) ,we have

(dy)/(dx)=8^(3^(x^2))3^(x^2)ln8(2xln3)

=>(dy)/(dx)=ln3*ln8*2x(3^(x^2)*8^(3^(x^2)))

In short :
y=8^(3^(x^2))
=>(dy)/(dx)=8^(3^(x^2))*ln8d/(dx)(3^(x^2))
=>(dy)/(dx)=8^(3^(x^2))*ln8{3^(x^2)ln3d/(dx)(x^2)}
=>(dy)/(dx)=8^(3^(x^2))*ln8{3^(x^2)ln3(2x)}
=>(dy)/(dx)=ln3*ln8*2x(3^(x^2)*8^(3^(x^2)))