2. Consider the function f(x)=3cos⁡(e5x−3)+4xf(x) = 3\cos(e^{5x-3}) + \frac{4}{x} Find f′(x)f'(x) [ddx(cos⁡x)=−sin⁡x]\left[\frac{d}{dx}(\cos x) = -\sin x\right]

Answer: f′(x)=−15e5x−3sin⁡(e5x−3)−4x2f'(x) = -15e^{5x-3}\sin(e^{5x-3}) - \frac{4}{x^2}

Step-by-step solution

Step 1: Apply linearity of differentiation

By the sum rule and constant multiple rule of differentiation, the derivative of a sum is the sum of the derivatives. We separate the expression into the trigonometric term and the rational term.

Step 2: Differentiate the first term using the chain rule

We use the chain rule for the composite function 3cos⁡(u)3\cos(u), where u=e5x−3u = e^{5x-3}. The derivative of cos⁡(u)\cos(u) with respect to uu is −sin⁡(u)-\sin(u), which we then multiply by the derivative of the inner function uu.

Step 3: Differentiate the inner exponential function

Applying the chain rule once more to the inner function e5x−3e^{5x-3}, the derivative of eve^v is ev⋅dvdxe^v \cdot \frac{dv}{dx}. Here v=5x−3v = 5x - 3, and its derivative with respect to xx is 55.

Step 4: Differentiate the second term and combine results

For the second term, we rewrite 4x\frac{4}{x} as 4x−14x^{-1} and apply the power rule: ddx(x−1)=−1⋅x−2=−1x2\frac{d}{dx}(x^{-1}) = -1 \cdot x^{-2} = -\frac{1}{x^2}. Multiplying by 44 yields −4x2-\frac{4}{x^2}.

Step 5: Combine and simplify to find f′(x)f'(x)

Multiplying 3⋅(−sin⁡(e5x−3))⋅5e5x−33 \cdot (-\sin(e^{5x-3})) \cdot 5e^{5x-3} gives −15e5x−3sin⁡(e5x−3)-15e^{5x-3}\sin(e^{5x-3}). Combining this with the derivative of the second term gives the complete expression for f′(x)f'(x).

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