Question #217eb

1 Answer
Nov 30, 2016

f'(x) = (sin^2x + sinx + xcosx)/(1 + sinx)^2

Explanation:

First of all, the function can be simplified.

Call the function f(x).

f(x) = (xtanx)/(1/cosx + sinx/cosx)

f(x) = (xtanx)/((1 + sinx)/cosx)

f(x) = (xtanx(cosx))/(1 + sinx)

f(x) = (xsinx/cosx(cosx))/(1 + sinx)

f(x) = (xsinx)/(1 + sinx)

We now differentiate this using the quotient rule. The quotient rule states that for a function color(red)(f(x) = (g(x))/(h(x)), the derivative is given by color(red)(f'(x) = (g'(x) xx h(x) - g(x) xx h'(x))/(h(x))^2. We know the derivative of the numerator is sinx + xcosx (by the product rule), and that the derivative of the denominator is cosx.

Hence:

f'(x) = ((sinx + xcosx)(1 + sinx) - xsinxcosx)/(1 + sinx)^2

f'(x) = (sinx + xcosx+ sin^2x + xcosxsinx - xcosxsinx)/(1 + sinx)^2

f'(x) = (sin^2x + sinx + xcosx)/(1 + sinx)^2

Hopefully this helps!