Identify function: Identify the function to differentiate.We are given the function f(x)=−5cos(7x−1) and we need to find its derivative with respect to x.
Apply chain rule: Apply the chain rule for differentiation.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. In this case, the outer function is −5cos(u) and the inner function is u=7x−1.
Differentiate outer function: Differentiate the outer function with respect to the inner function.The derivative of −5cos(u) with respect to u is 5sin(u), because the derivative of cos(u) is −sin(u) and we have a constant multiplier of −5.
Differentiate inner function: Differentiate the inner function with respect to x. The derivative of u=7x−1 with respect to x is 7, because the derivative of a constant is 0 and the derivative of 7x with respect to x is 7.
Apply chain rule multiplication: Apply the chain rule by multiplying the derivatives from Step 3 and Step 4.The derivative of f(x) with respect to x is the product of the derivatives from Step 3 and Step 4, which is 5sin(7x−1)×7.
Simplify expression: Simplify the expression.Multiplying 5 by 7 gives us 35, so the derivative of f(x) with respect to x is 35sin(7x−1).
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