Part of CALC-01 — Limits & Continuity

JEE Previous Year Patterns Analysis

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Pattern 1: 1^infinity Form (Appears almost every year) Questions like lim(x->0) [sinxx\frac{sin x}{x}]^(1/x2x^2) or lim(x->inf) [x+a(x+b)\frac{x+a}{(x+b)}]^(cx). Always apply the formula e^(lim g(x)*(f(x)-1)).

Pattern 2: Piecewise Function Continuity (Very frequent) Given f(x) defined in pieces, find parameter k for continuity at junction. Method: equate LHL = RHL = f(junction).

Pattern 3: Taylor-Based Limits (2-3 per year) Expressions like sinxx+x3/6x\frac{sin x - x + x^3/6}{x}^5 or ex1xx2/2x\frac{e^x - 1 - x - x^2/2}{x}^3. Expand using Taylor to the needed order.

Pattern 4: Riemann Sum to Integral (Once per year) Recognize 1n\frac{1}{n}*sum frn\frac{r}{n} = integral of f from 0 to 1. Common: 1n+r\frac{1}{n+r} terms, power sums.

Pattern 5: Greatest Integer Function Problems Find discontinuities of [f(x)], evaluate limits involving [x] or {x}. Requires careful one-sided analysis.

Pattern 6: L'Hopital with Parameter Finding If lim sinax+bsinxx\frac{sin ax + b*sin x}{x}^3 is finite, find a and b. Method: Taylor expand, set coefficients of lower powers to zero.

Pattern 7: Continuity-Differentiability Connection Given f defined with |x| or x*sin1x\frac{1}{x}, determine continuity and differentiability at x = 0. Remember: continuous does not imply differentiable.

Scoring Strategy:

  • Master the 1^infinity formula (guaranteed 1 question)
  • Practice piecewise continuity (guaranteed 1 question)
  • Learn Taylor expansions to x3x^3 term (handles most problems)
  • Know GIF/fractional part properties (1 question every other year)

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