Chapter 3: Problem 8
In Exercises find \(f^{\prime}(x)\). $$f(x)=\left(x^{2}+1\right) \sec x$$
Short Answer
Expert verified
The derivative is \(f'(x) = 2x \sec x + (x^2 + 1) \sec x \tan x\).
Step by step solution
01
Identify the Functions Involved
We have a product of two functions: \( u(x) = x^2 + 1 \) and \( v(x) = \sec x \). We need to differentiate \(f(x) = u(x)v(x)\).
02
Apply the Product Rule
The product rule states that the derivative of a product \(u(x)v(x)\) is given by \(f'(x) = u'(x)v(x) + u(x)v'(x)\). We will differentiate \(u(x)\) and \(v(x)\) separately.
03
Differentiate \(u(x) = x^2 + 1\)
The derivative of \(u(x) = x^2 + 1\) with respect to \(x\) is \(u'(x) = 2x\).
04
Differentiate \(v(x) = \sec x\)
The derivative of \(v(x) = \sec x\) with respect to \(x\) is \(v'(x) = \sec x \tan x\).
05
Substitute Derivatives into Product Rule
Using the product rule formula, substitute in the derivatives: \[f'(x) = (2x)(\sec x) + (x^2 + 1)(\sec x \tan x)\]
06
Simplify the Expression
Simplify the expression from the product rule: \[f'(x) = 2x \sec x + (x^2 + 1) \sec x \tan x\]. Keep it in this form, as it's already expanded.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Product Rule in Differentiation
Differentiation often deals with a wide range of functions, including those that are products of simpler functions. The product rule is a key differentiation technique that helps in finding the derivative of a product of two functions. When you have two functions, say \( u(x) \) and \( v(x) \), their product \( f(x) = u(x)v(x) \) can be differentiated using the product rule. The rule gives us that the derivative \( f'(x) \) is:
- \( f'(x) = u'(x)v(x) + u(x)v'(x) \)
- First, differentiate the first function \( u(x) \), multiply it by the second function \( v(x) \).
- Then, differentiate the second function \( v(x) \), multiply it by the first function \( u(x) \).
- Sum these two results together.
Understanding the Derivative of Secant
The function \( \sec x \), the secant function, is one that appears frequently in calculus. Its derivative has a specific form that is useful to remember:
- \( \frac{d}{dx} [\sec x] = \sec x \tan x \)
- Recall \( \sec x = \frac{1}{\cos x} \).
- This means the derivative can initially be found using the quotient rule but simplifies to \( \sec x \tan x \).
Differentiation Techniques Overview
The process of differentiation is foundational in calculus and involves finding how a function changes as its input changes. Differentiation techniques help solve a wide range of problems:
- The product rule is essential for functions that are products of other functions, as seen in the provided exercise.
- The chain rule is used when differentiating compositions of functions.
- The quotient rule applies when you have a function that is a division of two others.