Derivative Rules - 3.2 | Chapter 3: Calculus | ICSE Class 12 Mathematics
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Interactive Audio Lesson

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Power Rule

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Teacher
Teacher

Initially, let’s discuss the Power Rule. If we have a function of the form f(x) = x^n, who can tell me what the derivative looks like?

Student 1
Student 1

Is it something like d/dx[x^n] = n * x^(n-1)?

Teacher
Teacher

Exactly! So, if f(x) = x^3, can anyone find f'(x)?

Student 2
Student 2

That would be 3x^2!

Teacher
Teacher

Great job! A mnemonic to remember this is 'Drop and Multiply', where you drop the exponent and multiply it by the base reduced by one. Let’s move to the next rule.

Sum Rule

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Teacher
Teacher

Now, let’s look at the Sum Rule. When you differentiate a sum of functions, what happens?

Student 3
Student 3

We just differentiate each function separately and add the results?

Teacher
Teacher

Exactly! d/dx[f(x) + g(x)] = f'(x) + g'(x). Can you apply this to f(x) = x^2 + 3x?

Student 4
Student 4

So, f'(x) would be 2x + 3!

Teacher
Teacher

Right again! Remember, just differentiate each part separately. Let’s advance to the Product Rule.

Product Rule

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Teacher
Teacher

Next is the Product Rule. When differentiating a product of two functions, what should we do?

Student 1
Student 1

You differentiate the first function and multiply it by the second function, and then add the first function multiplied by the derivative of the second?

Teacher
Teacher

Exactly, it’s g'(x)h(x) + g(x)h'(x). Can anyone give me an example?

Student 2
Student 2

For f(x) = x^2 * sin(x), f'(x) would be 2x * sin(x) + x^2 * cos(x)!

Teacher
Teacher

Correct! Always remember to apply both functions in that formula. Let’s explore the Quotient Rule next.

Quotient Rule

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Teacher
Teacher

The Quotient Rule is next! Can someone detail how we differentiate a function that is a quotient?

Student 3
Student 3

We use (g'(x)h(x) - g(x)h'(x)) / h(x)^2?

Teacher
Teacher

Fantastic! Suppose we have f(x) = x^2/(x + 1). What’s the derivative?

Student 4
Student 4

That would be [2x(x + 1) - x^2(1)] / (x + 1)^2!

Teacher
Teacher

Exactly! Just remember, it’s crucial to keep the denominator squared in the result.

Chain Rule

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Teacher
Teacher

Lastly, let’s discuss the Chain Rule. What’s the process when differentiating composite functions?

Student 1
Student 1

You take the derivative of the outer function and multiply it by the derivative of the inner function?

Teacher
Teacher

Correct! d/dx[f(g(x))] = f'(g(x))g'(x). Can anyone provide an example?

Student 2
Student 2

For f(x) = sin(x^2), the derivative would be cos(x^2) * 2x!

Teacher
Teacher

Excellent! Always make sure to identify both layers of your composite function. Let’s recap what we learned today!

Introduction & Overview

Read a summary of the section's main ideas. Choose from Basic, Medium, or Detailed.

Quick Overview

This section covers the fundamental rules for differentiating various types of functions.

Standard

The derivative rules outlined in this section, including the Power Rule, Sum Rule, Product Rule, Quotient Rule, and Chain Rule, are essential tools for calculating the derivatives of different functions, providing crucial insight into how functions change.

Detailed

Derivative Rules

In calculus, understanding how to differentiate functions is vital. This section introduces several primary derivative rules that streamline the process of finding derivatives for various functions. The five key rules discussed are:

  1. Power Rule: Used for functions of the form f(x) = x^n, where the derivative is given by d/dx[x^n] = n * x^(nβˆ’1).
  2. Example: For f(x) = x^3, the derivative is f'(x) = 3x^2.
  3. Sum Rule: Applies when differentiating the sum of two functions: d/dx[f(x) + g(x)] = f'(x) + g'(x).
  4. Example: For f(x) = x^2 + 3x, the derivative is f'(x) = 2x + 3.
  5. Product Rule: Used for the product of two functions f(x) = g(x)h(x), resulting in d/dx[f(x)] = g'(x)h(x) + g(x)h'(x).
  6. Example: For f(x) = x^2 * sin(x), the derivative is f'(x) = 2x * sin(x) + x^2 * cos(x).
  7. Quotient Rule: This rule applies to the division of two functions. If f(x) = g(x)/h(x), then:
  8. d/dx[f(x)] = (g'(x)h(x) - g(x)h'(x)) / (h(x))^2.
  9. Example: For f(x) = x^2/(x + 1), the derivative is f'(x) = (2x(x + 1) - x^2(1)) / (x + 1)^2.
  10. Chain Rule: Used when differentiating composite functions: d/dx[f(g(x))] = f'(g(x)) * g'(x).
  11. Example: For f(x) = sin(x^2), we have f'(x) = cos(x^2) * 2x.

These rules provide a structured approach to differentiation and are fundamental in solving various calculus problems.

Audio Book

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Power Rule

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If 𝑓(π‘₯) = π‘₯𝑛, where 𝑛 is a constant, then
\[ \frac{d}{dx}[x^n] = n x^{n-1} \]
Example: 𝑑 [π‘₯Β³] = 3π‘₯Β².

Detailed Explanation

The Power Rule is a fundamental rule in differentiation that explains how to find the derivative of power functions. If a function is in the form of 𝑓(π‘₯) = π‘₯ raised to some constant power 𝑛, the derivative is calculated by multiplying the original exponent 𝑛 by the base π‘₯ raised to the exponent reduced by 1. For instance, if you have x^3, applying this rule gives you 3xΒ² (where you multiply by 3 and decrease the exponent from 3 to 2).

Examples & Analogies

Imagine a box with a square base whose area you want to maximize. If the side of the base is π‘₯, then the area is 𝑓(π‘₯) = π‘₯Β². To find how fast the area changes as you slightly change the side length, you'd use the Power Rule. If you differentiate, you'll find out how sensitive the area is to changes in the side length.

Sum Rule

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If 𝑓(π‘₯) = 𝑔(π‘₯) + β„Ž(π‘₯), then
\[ \frac{d}{dx}[f(x)] = \frac{d}{dx}[g(x)] + \frac{d}{dx}[h(x)] \]
Example: 𝑑 [π‘₯Β² + 3π‘₯] = 2π‘₯ + 3.

Detailed Explanation

The Sum Rule states that the derivative of a sum of functions is the sum of their derivatives. This means if you have two functions 𝑔(π‘₯) and β„Ž(π‘₯), and you want to find the derivative of their sum, all you need to do is differentiate each function individually and then add the results together. For example, if you are calculating the derivative of π‘₯Β² + 3π‘₯, you would derive π‘₯Β² to get 2π‘₯ and derive 3π‘₯ to get 3, thus summing these gives you the final result of 2π‘₯ + 3.

Examples & Analogies

Consider calculating costs for making a product where you have raw material costs and labor costs. If the material cost is represented by a function 𝑔(π‘₯) and labor cost is represented by β„Ž(π‘₯), the total cost at any production level is the sum of these two costs. To find how costs change as production increases, you’d apply the Sum Rule to find the total cost change.

Product Rule

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If 𝑓(π‘₯) = 𝑔(π‘₯)β„Ž(π‘₯), then
\[ \frac{d}{dx}[f(x)] = g'(x)h(x) + g(x)h'(x) \]
Example: 𝑑 [π‘₯Β² β‹… sin(π‘₯)] = 2π‘₯ sin(π‘₯) + xΒ² cos(π‘₯).

Detailed Explanation

The Product Rule is used when differentiating a function that is the product of two other functions. According to this rule, the derivative is not simply the product of the derivatives; instead, you need to take the derivative of the first function, multiply it by the second function, and then add the product of the first function and the derivative of the second function. For example, if you differentiate π‘₯Β² β‹… sin(π‘₯), you first differentiate π‘₯Β² (which gives you 2π‘₯), and multiply it by sin(π‘₯), then add the product of π‘₯Β² and the derivative of sin(π‘₯) (which is cos(π‘₯)) yielding the complete derivative.

Examples & Analogies

Think of mixing two ingredients for a cake, say flour and sugar. The overall weight of the cake (function) can be considered a product of the weights of the individual ingredients. If you want to understand how changing the amount of flour or sugar affects the total weight of the cake, you'd use the Product Rule to calculate this change effectively.

Quotient Rule

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If 𝑓(π‘₯) = \frac{g(π‘₯)}{β„Ž(π‘₯)} then
\[ \frac{d}{dx}[f(x)] = \frac{g'(x)h(x) - g(x)h'(x)}{[h(x)]^2} \]
Example: \[ \frac{d}{dx}\left[ \frac{x^2}{x+1} \right] = \frac{2x(x+1) - x^2(1)}{(x+1)^2}. \]

Detailed Explanation

The Quotient Rule applies when differentiating functions that are in a quotient (division) form. It states that if 𝑓(π‘₯) is the quotient of two functions 𝑔(π‘₯) and β„Ž(π‘₯), the derivative is found by taking the derivative of the numerator, multiplying it by the denominator, subtracting the product of the numerator and the derivative of the denominator, all divided by the square of the denominator. This helps in maintaining clear relationships even when a function is divided by another. For example, with 𝑔(π‘₯) = π‘₯Β² and β„Ž(π‘₯) = π‘₯ + 1, applying the quotient rule correctly yields the required derivative.

Examples & Analogies

Imagine you are analyzing speed as a ratio of distance to time. If distance varies with time, to find how fast speed changes overall when either distance (numerator) or time (denominator) changes, you would apply the Quotient Rule to calculate the changes effectively.

Chain Rule

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If a function is composed of two or more functions, say 𝑓(π‘₯) = 𝑔(β„Ž(π‘₯)), then
\[ \frac{d}{dx}[f(x)] = g'(h(x)) \cdot h'(x) \]
Example: \[ rac{d}{dx}[sin(x^2)] = cos(x^2) \cdot 2x. \]

Detailed Explanation

The Chain Rule is crucial for differentiating composite functionsβ€”functions made from one function nested inside another. To apply the Chain Rule, you differentiate the outer function first, then multiply it by the derivative of the inner function. For example, if you need to find the derivative of sin(π‘₯Β²), you first differentiate sin(𝑓) to get cos(𝑓), and then you multiply that by the derivative of the inner function π‘₯Β² (which is 2π‘₯). This properly captures how both layers of the function affect the rate of change.

Examples & Analogies

Think of a two-step recipe where you first mix ingredients (inner function) and then bake them (outer function). If you want to assess how changing an ingredient affects the final result, you'd need to know how each aspect influences the overall processβ€”just like applying the Chain Rule helps elucidate layered functions.

Definitions & Key Concepts

Learn essential terms and foundational ideas that form the basis of the topic.

Key Concepts

  • Power Rule: A fundamental rule for differentiating powers of x.

  • Sum Rule: The derivative of a sum is the sum of the derivatives.

  • Product Rule: A formula to differentiate products of functions.

  • Quotient Rule: A method for differentiating the division of two functions.

  • Chain Rule: A tool for differentiating composite functions.

Examples & Real-Life Applications

See how the concepts apply in real-world scenarios to understand their practical implications.

Examples

  • Using the power rule, if f(x) = x^4, then f'(x) = 4x^3.

  • For f(x) = x^2 + 5, applying the sum rule gives f'(x) = 2x.

Memory Aids

Use mnemonics, acronyms, or visual cues to help remember key information more easily.

🎡 Rhymes Time

  • To find the rate for x to the n, drop the n, count back down, then you can.

πŸ“– Fascinating Stories

  • Imagine a climbing mountain. The higher you go, the steeper it feelsβ€”like finding the slope through calculus and using the power rule to navigate down!

🧠 Other Memory Gems

  • Silly Penguins Prefer Quick Cuddles (Sum, Power, Product, Quotient, Chain).

🎯 Super Acronyms

SPPQC - Sum, Power, Product, Quotient, Chain.

Flash Cards

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Glossary of Terms

Review the Definitions for terms.

  • Term: Derivative

    Definition:

    A measure of how a function changes as its input changes.

  • Term: Power Rule

    Definition:

    A rule for differentiating functions of the form f(x) = x^n.

  • Term: Sum Rule

    Definition:

    A rule that states the derivative of a sum of functions is the sum of their derivatives.

  • Term: Product Rule

    Definition:

    A method for finding the derivative of the product of two functions.

  • Term: Quotient Rule

    Definition:

    A method for finding the derivative of the quotient of two functions.

  • Term: Chain Rule

    Definition:

    A technique for differentiating composite functions.