JEE Main Maths · Limits, Continuity & Differentiability PYQ
JEE Main Limits, Continuity & Differentiability PYQ (2002–2025)
Limits, Continuity & Differentiability is a P1 Calculus-foundation chapter — ~7% JEE Main weightage with 2 questions per paper. It's the conceptual gateway to Differentiation and Integration — strong fluency here cascades into the rest of Calculus.
Limits, Continuity & Differentiability PYQs from 2002 to 2025 covering evaluation techniques (L'Hôpital, standard limits, Taylor expansion), continuity at a point, differentiability, and problems combining the three concepts. Every KaTeX-rendered solution names the technique upfront.
Limits, Continuity & Differentiability at a Glance
Key Sub-Topics & What's Tested
Standard Limits
lim(x→0) sin x / x = 1, lim(x→0) (1 - cos x)/x² = 1/2, lim(x→∞) (1 + 1/x)^x = e, lim(x→0) (aˣ - 1)/x = ln a.
Evaluation Techniques
Direct substitution, factoring, rationalising, L'Hôpital's rule for 0/0 and ∞/∞, Taylor series expansion.
L'Hôpital's Rule
For 0/0 or ∞/∞ forms, lim f(x)/g(x) = lim f'(x)/g'(x). Apply iteratively until indeterminate form resolves.
Trigonometric Limits
Limits involving sin, cos, tan near 0; using sin x ≈ x, cos x ≈ 1 - x²/2 for small angles.
Exponential & Logarithmic Limits
Limits using eˣ = 1 + x + x²/2 + ..., ln(1+x) = x - x²/2 + ..., for small x.
Continuity at a Point
Three conditions: f(a) defined, lim(x→a) f(x) exists, both equal. LHL = RHL = f(a).
Differentiability at a Point
LHD = RHD at x = a. Differentiability implies continuity but not vice versa.
Piecewise Functions
Checking continuity and differentiability at boundary points of piecewise-defined functions — very common PYQ template.
Question Type Distribution
| Question Type | Share (approx) | Example Pattern |
|---|---|---|
| Limit Evaluation (Algebraic) | 20% | Evaluate lim(x→2) (x² - 4)/(x - 2) using factoring. |
| L'Hôpital Application | 25% | Evaluate lim(x→0) (sin x - x)/x³ using L'Hôpital twice. |
| Trigonometric Limits | 20% | Evaluate lim(x→0) (1 - cos 2x)/(x sin x). |
| Exponential/Logarithmic Limits | 10% | Evaluate lim(x→∞) (1 + 2/x)^(3x). |
| Continuity Verification | 15% | For f(x) = {x² if x<1; ax + b if x≥1}, find a and b such that f is differentiable at x = 1. |
| Differentiability at a Point | 10% | Check if f(x) = |x³| is differentiable at x = 0. |
How to Solve Limits, Continuity & Differentiability PYQs
- 1Memorise 10 standard limits. sin x/x → 1, (1-cos x)/x² → 1/2, tan x/x → 1, (eˣ-1)/x → 1, ln(1+x)/x → 1, (1+1/x)^x → e, (1+x)^(1/x) → e. Direct recall saves 90 seconds per question.
- 2Check indeterminate form first. If direct substitution gives 0/0, ∞/∞, 0·∞, ∞-∞, use L'Hôpital or algebraic manipulation. Otherwise, direct substitution works.
- 3For piecewise functions, use LHL and RHL. Evaluate f(a-h) and f(a+h) separately, equate for continuity. For differentiability, evaluate LHD and RHD.
- 4Taylor series for hard limits. Expand sin x = x - x³/6 + ..., cos x = 1 - x²/2 + ..., eˣ = 1 + x + x²/2 + .... Keep terms up to needed order.
- 5Differentiability implies continuity, not vice versa. |x| is continuous at 0 but not differentiable. This concept drives many trick PYQs.
Common Mistakes That Cost Marks
- Applying L'Hôpital to non-indeterminate forms. lim(x→0) (sin x)/x² is 0/0 at first glance, but becomes cos(x)/2x after L'Hôpital — still needs care. Always verify form.
- Forgetting to check both LHL and RHL. A limit exists only if LHL = RHL = a finite number. If they differ, limit does not exist.
- Confusing f(a) with lim f(x) at x = a. f(a) is the function value. lim f(x) is the limit. Continuity requires both to exist and be equal.
- Using Taylor series without enough terms. For lim (sin x - x)/x³, you need sin x = x - x³/6 + O(x⁵). Using only x - x³/6 gives answer -1/6; using just sin x ≈ x gives 0 (wrong).
- Assuming differentiable → continuous works both ways. Continuous does NOT imply differentiable. Function must have no sharp corners or cusps for differentiability.
Related JEE Main Practice
Frequently asked questions
How many Limits PYQs should I solve?
Target 60–80 PYQs across 2010–2025. At ~7% weightage, Limits is a high-ROI chapter. The standard-limit patterns are highly repetitive — volume builds instant recall.
When should I use L'Hôpital vs Taylor series?
L'Hôpital: for straightforward 0/0 or ∞/∞ where derivatives are easy. Taylor series: for limits involving sin, cos, ln, eˣ near 0 — more elegant and often faster.
Are Limits PYQs harder than Differentiation PYQs?
Comparable difficulty but different flavours. Limits are more pattern-recognition. Differentiation has more mechanical chain-rule application with maxima-minima twists.
What's the most-tested Limits PYQ pattern?
Trigonometric limits near 0 with small-angle approximations — lim (1-cos ax)/(1-cos bx) type. Roughly 4–5 variants per 10-year window.
How do I verify continuity quickly in PYQs?
For piecewise function at x = a: compute f(a), compute LHL (from x = a-h, h→0), compute RHL (from x = a+h, h→0). All three equal → continuous. Any mismatch → discontinuous.
Does Limits connect to Integration PYQs?
Yes — definite integrals as limits of sums (Riemann sum interpretation) appears in a few PYQs per 10-year window. Foundation for understanding Integration rigorously.
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