Solving Limits: Expansion Method

Duration: 14 min

This video lesson is available to enrolled students.

Return to /learn/COAL-INDIA-MANAGEMENT-TRAINEE/engineering-maths/calculus/limits/asset-solving-limits-expansion-method after enrolling

Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. Paper-2 | Programming & Data Structures: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling, Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  3. Paper-2 | Databases / DBMS & SQL: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Relational Calculus, Transaction Management, Concurrency Control
  4. Paper-2 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos
  5. Paper-2 | Computer Networks & Security: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware Basics, Network Access Technologies, Network Security
  6. Paper-2 | Digital Logic: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation, Floating Point Rep
  7. Paper-2 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  8. Paper-2 | Theory of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines
  9. Paper-2 | Computer Organization & Architecture: Basics of COA, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Control Unit Design, Programming the Basic Computer
  10. Paper-2 | Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  11. Paper-1 | General Awareness: Polity, Physics, Biology, Chemistry, Static General Knowledge, GK- Current Affairs, History, Geography, Indian Economy, Environment
  12. Paper-1 | Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Data Interpretation, Blood Relations, Syllogisms, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Selection Decision Table (Decision Making), Clock, Calendar, Cubes & Dices, Directions (Direction Test), Analogy, Seating Arrangements, Analytical Reasoning (Counting Figures Reasoning)
  13. Paper-1 | Quantitative Aptitude: Ratio and Proportion (Ratios), Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Speed Time and Distance, Average, Age Problems, Percentage, Profit and Loss, Time and Work, Pipe and Cistern, Simple Interest and Compound Interest, Powers and Exponents (Surds and Indices), Mensuration and Geometry, Probability, Statistics, Arithmetic, Algebra
  14. Paper-1 | English: Vocabulary, Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Construction, Cloze Test (Cloze Passage)
  15. Coal India Previous Year Paper:
  16. Engineering Mathematics: Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Linear Algebra, Calculus
  17. Coal India Mock Test:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video is a comprehensive calculus lecture by Yash Jain Sir, focusing on the topic of series expansions, specifically Taylor and Maclaurin series. The instructor systematically presents standard expansions for logarithmic, exponential, and trigonometric functions on a whiteboard. He then transitions to a computer screen to show the theoretical background from Wikipedia before returning to the board to solve complex limit problems. The core of the lesson demonstrates how substituting these infinite series allows for the efficient evaluation of indeterminate limits that result in 0/0 forms, avoiding the need for repeated differentiation.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with a title card featuring the word 'CALCULUS' surrounded by various mathematical equations. The scene then cuts to a whiteboard with the heading 'EXPANSION' written in red. The instructor, Yash Jain Sir, introduces the first set of standard series expansions. He points to the formula for the natural logarithm of one plus x, written as log(1+x) = x - x^2/2 + x^3/3 - x^4/4 + .... He follows this with the expansion for log(1-x), which is -x - x^2/2 - x^3/3 - x^4/4 - .... He then lists the exponential expansions: e^x = 1 + x + x^2/2! + x^3/3! + ... and e^-x = 1 - x + x^2/2! - x^3/3! + .... These formulas are written clearly in black marker for the students to copy.

  2. 2:00 – 5:00 02:00-05:00

    The instructor continues filling the whiteboard with the remaining standard expansions. He writes the series for sine as sin x = x - x^3/3! + x^5/5! - x^7/7! + ... and cosine as cos x = 1 - x^2/2! + x^4/4! - x^6/6! + .... He also includes the expansion for tangent, tan x = x + x^3/3 + 2x^5/15 + ..., and the general exponential form a^x = 1 + x ln a + (x ln a)^2/2! + .... After listing these, the video switches to a computer screen where the instructor performs a Google search for 'taylor series wikipedia'. He navigates to the Wikipedia page, scrolling through the text to show the general definition of a Taylor series and its relation to derivatives. He highlights sections on the exponential function and natural logarithm to reinforce the formulas on the board.

  3. 5:00 – 10:00 05:00-10:00

    The lesson moves to practical application with the first limit problem: lim x->0 (sin x - x + x^3/6) / x^5. The instructor writes the expansion for sin x on the right side of the board. He substitutes this series into the numerator of the limit expression. The expression becomes (x - x^3/3! + x^5/5! - x^7/7! + ...) - x + x^3/6. He carefully cancels the x term with the -x and the -x^3/6 term with the +x^3/6 (since 3! is 6). This leaves x^5/5! - x^7/7! + ... in the numerator. He divides the entire expression by x^5, factoring it out to get 1/5! - x^2/7! + .... As x approaches 0, all terms with x vanish, leaving the final answer of 1/120.

  4. 10:00 – 13:32 10:00-13:32

    The instructor solves two additional limit problems to reinforce the concept. The second problem is lim x->0 (sin x + log(1-x)) / x^2. He substitutes the expansions for both functions: (x - x^3/3! + ...) + (-x - x^2/2 - x^3/3 - ...). The x terms cancel out, leaving -x^2/2 as the dominant term in the numerator. Dividing by x^2 gives a limit of -1/2. The final problem is lim x->0 (e^x + e^-x - 2 - x^2) / x^4. He substitutes the expansions for e^x and e^-x. The constants 1 + 1 cancel with -2. The linear terms x - x cancel. The quadratic terms x^2/2! + x^2/2! cancel with -x^2. This leaves x^4/4! + x^4/4! in the numerator. Simplifying 2/4! gives 2/24, which reduces to 1/12. The video concludes with a 'THANKS FOR WATCHING' screen.

This lecture provides a structured approach to solving indeterminate limits using series expansions. By first establishing the theoretical foundation through standard formulas and Wikipedia references, the instructor ensures students understand the origin of the series. The step-by-step walkthrough of three distinct limit problems demonstrates the power of this method, showing how higher-order terms can be ignored and lower-order terms cancelled to find the limit quickly. This technique is presented as a superior alternative to L'Hopital's rule for complex functions.

Loading lesson…