Q. Let f(x)=2cos(2x).Find f′′(x).Choose 1 answer:(A) −cos(2x)(B) −sin(2x)(C) −8cos(2x)(D) −21cos(2x)
Differentiate function f(x): Differentiate the function f(x)=2cos(2x) with respect to x to find the first derivative f′(x). Using the chain rule, the derivative of cos(u) with respect to x is −sin(u) times the derivative of u with respect to x. Here, u=2x, so the derivative of u with respect to x is f(x)=2cos(2x)2. f(x)=2cos(2x)3
Simplify first derivative: Simplify the expression for the first derivative. f′(x)=−sin(2x)
Differentiate f′(x): Differentiate the first derivative f′(x)=−sin(2x) with respect to x to find the second derivative f′′(x). Using the chain rule again, the derivative of −sin(u) with respect to x is −cos(u) times the derivative of u with respect to x. Here, u=2x, so the derivative of u with respect to x is f′(x)=−sin(2x)2. f′(x)=−sin(2x)3
Simplify second derivative: Simplify the expression for the second derivative. f′′(x)=−(21)cos(2x)
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