Chapter 8: Problem 19
Differentiate each function. $$ f(t)=\cos (t+\pi)^{3} $$
Short Answer
Expert verified
The derivative is \( f'(t) = -3(t+\pi)^2 \sin((t+\pi)^3) \).
Step by step solution
01
Recognize the Function Structure
The function given is \( f(t) = \cos (t + \pi)^3 \). This can be viewed as a composite function, where the outer function is \( \cos(x) \) and the inner function is \( (t+\pi)^3 \).
02
Find the Derivative of the Outer Function
According to the chain rule, differentiate the outer function \( \cos(u) \) with respect to \( u \). The derivative of \( \cos(u) \) is \( -\sin(u) \).
03
Differentiate the Inner Function
Next, differentiate the inner function \( (t+\pi)^3 \) with respect to \( t \). Apply the power rule: \( \frac{d}{dt}((t+\pi)^3) = 3(t+\pi)^2 \).
04
Apply the Chain Rule
Using the chain rule, multiply the derivative of the outer function by the derivative of the inner function: \( \frac{df}{dt} = -\sin((t+\pi)^3) \times 3(t+\pi)^2 \).
05
Write the Final Derivative Expression
Combine all parts to get the derivative: \( f'(t) = -3(t+\pi)^2 \sin((t+\pi)^3) \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Chain Rule
The Chain Rule is a fundamental tool in calculus used to find the derivative of composite functions. When dealing with functions composed of multiple layers, we need a strategy to differentiate them. This is where the Chain Rule shines.
Imagine you have a function that's built like an onion: layers upon layers. The Chain Rule helps you peel back these layers, starting from the outermost to the innermost, to find the derivative.
When you look at a composite function, you'll notice two main pieces:
- The outer function, which you handle first
- The inner function, which follows after
- Dive into the outer layer, taking its derivative, and leave the inside unchanged temporarily.
- Slide down to the inner layer, compute its derivative as well.
- Multiply these derivatives to get the full derivative of the entire composite function.
Power Rule
The Power Rule is a basic but powerful tool in differentiating functions, especially polynomials. It provides a quick way to find the derivative of expressions with exponents.When you have a function like \[ (t + \pi)^3 \], the Power Rule lets you differentiate it effortlessly.Here's the simple process:
- Identify the exponent, which is 3 in this case.
- Bring down that exponent in front as a coefficient.
- Subtract one from the exponent.
Composite Function
A composite function is essentially a function within another function. It’s like having a "function sandwich," where the inner function provides output that the outer function then uses as its input.For instance, in our given problem, the function inside the cosine function:\[ (t + \pi)^3 \] serves as the inner layer. This entire expression is the input to the outer cosine function, which then processes it further.Recognizing a composite function is crucial for applying the Chain Rule effectively. Typically, composite functions are written as:\[ f(g(x)) \], where \[ f(x) \] is the outer function and \[ g(x) \] is the inner function.When working with composite functions, you need to:
- Identify each part of the function and understand their roles.
- Differentiated each part individually.
- Combine the derivatives using techniques like the Chain Rule to handle the composite nature.