How do you differentiate y= x^(11cosx)y=x11cosx?

1 Answer
May 30, 2018

dy/dx=11x^(11cos(x))(cos(x)/x-sin(x)ln(x))dydx=11x11cos(x)(cos(x)xsin(x)ln(x))

Explanation:

y=x^(11cos(x))y=x11cos(x)

To deal with tricky exponents like this, let's take the natural logarithm of both sides and remember the rule log(a^b)=blog(a)log(ab)=blog(a).

ln(y)=ln(x^(11cos(x)))ln(y)=ln(x11cos(x))

ln(y)=11cos(x)ln(x)ln(y)=11cos(x)ln(x)

Now take the derivative on both sides. On the left, we'll need the chain rule. On the right, we'll use the product rule.

1/y(dy/dx)=11(d/dxcos(x))ln(x)+11cos(x)(d/dxln(x))1y(dydx)=11(ddxcos(x))ln(x)+11cos(x)(ddxln(x))

1/y(dy/dx)=11(-sin(x))ln(x)+11cos(x)(1/x)1y(dydx)=11(sin(x))ln(x)+11cos(x)(1x)

Solving for the derivative:

dy/dx=y((11cos(x))/x-11sin(x)ln(x))dydx=y(11cos(x)x11sin(x)ln(x))

dy/dx=11x^(11cos(x))(cos(x)/x-sin(x)ln(x))dydx=11x11cos(x)(cos(x)xsin(x)ln(x))