Identify Outer Function: Identify the outer function and its derivative.The outer function is the cosine function, so we need to find the derivative of cos(u), where u is a function of x. The derivative of cos(u) with respect to u is −sin(u).
Identify Inner Function: Identify the inner function and its derivative.The inner function is 2ln(−4x−3). To find its derivative, we use the chain rule. The derivative of ln(v) with respect to v is 1/v, so the derivative of 2ln(v) is 2/v. Here, v=−4x−3, so the derivative of the inner function is 2/(−4x−3).
Apply Chain Rule: Apply the chain rule.The chain rule states that the derivative of a composite function is the derivative of the outer function evaluated at the inner function times the derivative of the inner function. So, we have:f′(x)=−sin(2ln(−4x−3))⋅(dxd)(2ln(−4x−3))
Differentiate Inner Function: Differentiate the inner function.We already found that the derivative of 2ln(−4x−3) is (−4x−3)2. Now we need to differentiate −4x−3 with respect to x, which is simply −4. So the derivative of the inner function is (−4x−3)2×−4.
Simplify Inner Function Derivative: Simplify the derivative of the inner function.Multiplying (−4x−3)2 by −4 gives us (−4x−3)−8, which simplifies to (−4x−3)8 because the negatives cancel out.
Combine Derivatives: Combine the derivatives to find the final derivative.Now we multiply the derivative of the outer function by the simplified derivative of the inner function:f′(x)=−sin(2ln(−4x−3))⋅(−4x−38)
Simplify Final Expression: Simplify the final expression.We can leave the final derivative in its current form, as it is already simplified:f′(x)=−8sin(2ln(−4x−3))/(−4x−3)
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