How do you find the derivative of tan^4 (x)tan4(x)?

1 Answer
May 19, 2017

By using the power rule

d/(dx)[(u(x))^n] = n [u(x)]^(n-1)ddx[(u(x))n]=n[u(x)]n1, where u(x)u(x) is a function of xx,

and the chain rule

d/(dx)[f(u)] = (df)/(du)(du)/(dx)ddx[f(u)]=dfdududx, where f = f(u(x))f=f(u(x)).

If we rewrite tan^4(x)tan4(x) as (tanx)^4(tanx)4, we have that:

  • f(u) = u^4f(u)=u4
  • u(x) = tanxu(x)=tanx

As a result:

color(blue)(d/(dx)[f(u)]) = (df)/(du)(du)/(dx)ddx[f(u)]=dfdududx

d/(du)[u^4]cdot d/(dx)[tanx]ddu[u4]ddx[tanx]

= 4u^3 cdot sec^2x=4u3sec2x

= color(blue)(4tan^3xsec^2x)=4tan3xsec2x