Chapter 3: Problem 12
Find the derivative. \(f(x)=3 x^{2} \sec x-x^{3} \tan x\)
Short Answer
Expert verified
The derivative is \(f'(x) = 6x \sec x + x^2 \sec x \tan x - x^3 \sec^2 x\).
Step by step solution
01
Identify the Parts for Differentiation
The function is given as sum (or difference) of two terms: \(3x^2 \sec x\) and \(x^3 \tan x\). We need to differentiate each term separately.
02
Differentiate the First Term
To differentiate \(3x^2 \sec x\), use the product rule. Let \(u = 3x^2\) and \(v = \sec x\).First, find the derivatives, \(u' = 6x\) and \(v' = \sec x \tan x\). Using the product rule: \[\frac{d}{dx}(uv) = u'v + uv' = 6x \sec x + 3x^2 \sec x \tan x\]
03
Differentiate the Second Term
For \(x^3 \tan x\), also use the product rule. Let \(u = x^3\) and \(v = \tan x\).Find the derivatives: \(u' = 3x^2\) and \(v' = \sec^2 x\).Using the product rule:\[\frac{d}{dx}(uv) = u'v + uv' = 3x^2 \tan x + x^3 \sec^2 x \]
04
Combine the Derivatives
The original function's derivative is the sum of the derivatives found in the previous steps:\[f'(x) = (6x \sec x + 3x^2 \sec x \tan x) - (3x^2 \tan x + x^3 \sec^2 x) \]Simplify the expression:\[f'(x) = 6x \sec x + 3x^2 \sec x \tan x - 3x^2 \tan x - x^3 \sec^2 x\]Combine like terms when possible.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Product Rule
In calculus, the product rule is a fundamental tool for differentiating products of functions. When you have two differentiable functions, say \( u \) and \( v \), and you want to find the derivative of their product \( uv \), the product rule provides a clear path:\[\frac{d}{dx}(uv) = u'v + uv'\]Here's how it unfolds practically:
- First, differentiate \( u \) to obtain \( u' \).
- Then, differentiate \( v \) to get \( v' \).
- Multiply \( u' \) by \( v \), and \( u \) by \( v' \).
- Finally, add the two resulting expressions together.
Trigonometric Differentiation
Trigonometric differentiation comes into play when your function involves trigonometric functions like \( \sec x \) or \( \tan x \). These functions have specific derivative rules you need to memorize:
- The derivative of \( \sec x \) is \( \sec x \tan x \).
- The derivative of \( \tan x \) is \( \sec^2 x \).
Calculus Problem-Solving
Solving calculus problems typically involves a series of logical and systematic steps. Here's a structured approach that you can apply when faced with a differentiation problem:
- **Identify Components:** Break down the complex function into simpler parts, as seen with \( 3x^2 \sec x \) and \( x^3 \tan x \).
- **Apply Rules Appropriately:** Use the product rule, chain rule, or quotient rule as needed, considering the specific function characteristics.
- **Simplify:** After differentiating, always look to simplify the derivative for a cleaner result. This involves combining like terms, factoring, or reducing expressions.